Question: What did Nirvana do differently with "In Utero" that caused a documentary to be made about recording the album?

Context articles: Dumb (Nirvana song)
Rape Me
In Utero, in Tribute, in Entirety
Whatever Nevermind
In Utero (album)
Pennyroyal Tea
Heart-Shaped Box
Nirvana – A Classic Album Under Review – In Utero
Razorblade Suitcase
Doused in Mud, Soaked in Bleach

"Dumb" is a song by American rock band Nirvana.
 It is the sixth song on the band's third studio album "In Utero", released in 1993.
"Rape Me" is a song by American rock band Nirvana, written by frontman Kurt Cobain.
 The song was released as the second single from Nirvana's third album "In Utero" in 1993, packaged as a double A-side along with "All Apologies".
 The single reached number 32 on the UK Singles Chart.
In Utero, in Tribute, in Entirety is a tribute album to Nirvana's 1993 third and final album, "In Utero", by various artists.
 The album was released through Robotic Empire on April 15, 2014, and an exclusive version was released for Record Store Day on April 19, 2014.
 The compilation, which represents Robotic Empire's 100th release overall and 15th anniversary as a business, took over 7 years to make because of "extended delays and legal wrangling."
 In the time it took to make the album, Jay Reatard died and These Arms Are Snakes, Thursday and Daughters disbanded (though the latter reformed shortly before the release), making their contributions some of the last music they recorded.
 An unmastered version of Jay Reatard's "Frances Farmer Will Have Her Revenge on Seattle" leaked online a few years prior to the official release of the album.
Whatever Nevermind is a tribute album to Nirvana's 1991 second studio album, "Nevermind", by various artists.
 The album was released by Robotic Empire for Record Store Day on April 18, 2015 in vinyl and digital formats.
 Robotic Empire previously released "In Utero, in Tribute, in Entirety" — a tribute to Nirvana's third and final studio album "In Utero" — for Record Store Day 2014.
 "Whatever Nevermind" also coincides with the label's 16th anniversary, and celebrates this fact by cataloging the album as the label's 116th release.
In Utero is the third and final studio album by American rock band Nirvana, released on September 21, 1993, by DGC Records.
 Nirvana intended the record to diverge significantly from the polished production of its previous album, "Nevermind" (1991).
 To capture a more abrasive and natural sound, the group hired engineer Steve Albini to record "In Utero" during a two-week period in February 1993 at Pachyderm Studio in Cannon Falls, Minnesota.
 The music was recorded quickly with few studio embellishments, and the song lyrics and album packaging incorporated medical imagery that conveyed frontman Kurt Cobain's outlook on his publicized personal life and his band's newfound fame.
"Pennyroyal Tea" is a song by the American rock band Nirvana.
 It is the ninth track on the band's third and final studio album, "In Utero" (1993).
 The song was due to be released as the third single from "In Utero" in April 1994.
 However, after the death of Kurt Cobain in the same month, the planned release was cancelled.
 The single was re-released on limited edition 7 inch vinyl for Record Store Day in April 2014 and charted at number 1 on the "Billboard" Hot 100 Singles Sales chart.
"Heart-Shaped Box" is a song by American rock band Nirvana, written by vocalist and guitarist Kurt Cobain.
 The song was released as the first single from the group's third and final studio album, "In Utero", in 1993.
 It was one of two songs from the album mixed by Scott Litt in order to augment the original production by producer Steve Albini.
 While Nirvana's label DGC Records did not release a physical single for sale in the United States, "Heart-Shaped Box" received much American radio airplay, reaching number one on the "Billboard" Modern Rock Tracks chart.
 The international release of the single reached number five on the UK Singles Chart.
 The song's music video, directed by Anton Corbijn, garnered critical plaudits, and won two awards, including Best Alternative Video at the MTV Video Music Awards in 1994.
Nirvana – A Classic Album Under Review – In Utero (also known as Nirvana's In Utero) is a 2006 music documentary released exclusively to DVD dealing with grunge band Nirvana's third studio album, "In Utero".
 The film purports to offer a "rare insight" into the influential music group, and consists of live and studio performances by Nirvana, interspersed with interviews with the band and with music industry notables and experts.
 It was released on November 21, 2006, and has a running time of 70 minutes.
Razorblade Suitcase is the second studio album by British rock band Bush, released on 19 November 1996, through Trauma Records.
 It was the follow up to their multi-platinum album "Sixteen Stone" and debuted at number one on the "Billboard" 200, selling 293,000 copies during its first week of release in the US.
 To date it remains the only Bush album to top the "Billboard" 200.
 Recorded at Abbey Road Studios in London with engineer/producer Steve Albini, the album's sound has been compared by many to Nirvana's "In Utero" album, which was also produced and engineered by Albini.
Doused in Mud, Soaked in Bleach is a tribute album to Nirvana's 1989 debut album, "Bleach", performed by various artists.
 The album was released by Robotic Empire for Record Store Day on April 16, 2016.
 It also concludes a series Robotic Empire Nirvana tribute albums, which also includes 2014's "In Utero, in Tribute, in Entirety" (a tribute to "In Utero") and "Whatever Nevermind" (a tribute to "Nevermind").