This is an interesting observation, but it's poorly contextualized, and becomes rather trite in the context of modern trends in melodic construction.

His attempts to contextualize this are not lacking: there's a hint at the minor third's use in schoolyard songs, a quintessential reference to the overtone series (the God of the gaps of armchair music theorists!) an appeal to Bernstein's The Unanswered Question (which is, sadly, for all its visionarity, bordering on irrelevance in the light of the intervening four decades of research on music perception), the quintessential appeal to the overtone series). There is no attempt to understand why the 'whoop' sounds good in songs, or how it relates to other trends in music. The mere identification of a pattern provides little insight into its usage and meaning. But who doesn't enjoy a few digs at the formulaic nature of pop?

Let's look at an example, from the article "Good Time". There's actually far more information density in pop music than is assumed.

Specifically, let's focus on the use of the 'whoop' as a way of delineating chorus activity. The article identifies the 'whoop' at 0:04, but this card-collecting example-finding behavior hides its main usage in the song.

A major 6-5 scale degree pattern predominates in the verses of "Good Time," often to start a phrase ("Woke up"; "What's up") or nested inside of other melodic patterns. Many phrases are ended with a descending 3-1-6, outlining a minor triad (or 1-6-5). All of these patterns avoid closure on the tonic, allowing for smooth elision into the next sentence.

To end the first half of the verse, Owl City uses a 3-5 pattern (the inverse of the 'whoop') at 'inside my head', followed by Jepsen humming 5-3-1, a foreshadowing of the 'whoop' in the chorus.

The 5-3 pattern takes over in the chorus. This fundamentally transforms how the 6-5 patterns at the ends of phrases are perceived. In the chorus, they are no longer a way of avoiding closure during the rapid declamation of the verses. They are fully subsumed as little moments of relaxation in between 'whoops' of freedom, joy, summer...in short, the joys of being a Millennial.

Among the myriad trends and styles that have enjoyed their moments of fame in the history of pop, the most notable is likely the tension between melodies and chord progressions based on the minor pentatonic scale (roughly, blues, rock, etc.) and those based on diatonic scales (arguably, the major pentatonic is stylistically aligned with this side). Different stylistic elements have predominated at various points in time.

There has been a resurgence in the popularity of certain diatonic patterns (especially those based on the diatonic major scale) in the past ten years. The 5-3 minor third is particularly useful as a bridge between the pentatonic and diatonic worlds. The 'Millennial Whoop' is no doubt an outgrowth of that trend. There has also been a trend for choruses to focus on the fifth scale degree, often in a higher pitch range than the surrounding verses (this is not remotely new, but in the past, was more identifiable by the use of V chords rather than melodic construction around the fifth scale degree).

As an example of the 5-3's usage elsewhere, Adele's Someone Like You, with its soulful roots and pentatonic construction, exemplifies many of the trends that are picked up in the 'whoop'. She starts many phrases in the verses with a descending 5-3 minor third, then moves to a higher pitch range for the chorus...with a few anguished (decidedly not feel-good and 'whoopy') minor thirds (e.g. "I beg").
(https://www.youtube.com/watch?v=1CGuafoq3T4)