As a regular user of the Javascript-less page, several months ago it started returning wildly different results than the “fully featured” version for the same queries. My uneducated guess is that it’s using a different index. There also appears to be some sort of rate-limiting wherein the results will frequently just be empty (using the JS version and same query resolves the issue).

I’m guessing they’re intentionally degrading the non-Javascript page as an anti-bot measure, but it’s so bad that I find it disingenuous to suggest that the non-Javascript page even a valid alternative at this point.