From LOC website:

"Note about deep paging limitations

Due to the technical limitations of search engine technologies, it is not recommended that users page through a large number of result pages. If the number of result pages is excessive, it will be better to use faceting or more specific search terms to reduce the result set. Paging past the 100,000th item in a search result is not supported at this time. In some searches, responses may fail before 100,000 items."

https://www.loc.gov/apis/json-and-yaml/

This is what the OP states:

"A misconception regarding Google's search results is that all of the results are being served to the user conducting that particular search. Those 2 billion search results can't be gotten through Google's pagination, and it seems that this number is somewhat arbitrary to the search, or commonality of the keyword."

That seems accurate. One cannot retrieve the full number of results. The parent demonstrated this with some examples.^1

The pertinent question IMO is how many results can one retrieve. As someone who started using www search engines in 1993, that number keeps shrinking. IMO, this is a reflection of companies like Google seeking to commercialise the web for their own benefit. Google wants the web and paid advertisement to be synonymous.

With Wikipedia or LOC, one can retrieve more results that one can using Google. More importantly, the sorting order (ranking) is different. Not sure about Wikipedia but no one uses "SEO" for LOC. It is a curated collection, unlike the uwashed web. In the pre-Google era, people would choose the name "Acme" for their businesses so they could be listed first in the Yellow Pages. Google does not allow alphabetical listing. The reader should be able to figure out why. It's because the web is not curated. It is not a library. Google is only interested in what sells advertising.

Using Google from the command line (no cookies, no Javascript)

"golang" 457 results max
"god" 576 results max
"america" 448 results max

Those numbers are laughable if one sees Google as some kind of "oracle" for open-ended questions, a gateway to the world's information, or even to the contents of the www, as many seem to do. It is not even close. It is a filter. The filter has a purpose. The purpose is commercial.

Of course Google is useful but one is kidding themselves if they believe Google is anything like a library. Libraries (public, academic) generally do not subsist on selling advertising services. Library websites and Google may use computers and similar software that have limitations but that does not mean they share the same principles. There is no reason to believe LOC would not serve all www users with more than 10000 results if the software allowed it. LOC is not promoting some results over others based on commercial objectives.

The parent may be referring to this recent HN comment allegedly from a former Google employee:

https://news.ycombinator.com/item?id=32785079

Google fans are happy if the reader conflates (a) technical limitations with (b) commercial objectives, e.g., "secret algorithms" for ranking results. Anyone using computers and software will be subject to (a) but not every entity using computers and software to assist patrons with searching its catalog (database) must engage in Google-like behaviour.

1.

YMMV, but I found Github would only return 90 results max for "golang" when searching from the command line (no cookies, no Javascript).

Wikipedia caps results at 10000. This is stated on the website.