Update 2022-09-19: I was right. Google only ever returns < 400 search results. It will not return more. Google search *is* broken and it is broken intentionally. The differences between being logged-in and logged-out are merely the number of results per page. Even while logged out no more than 400 results can ever be returned. RIP Google Search, 1998-2019.
I've also registered googlesearchonlyreturns400results.lol and put up a little placeholder explanation of the problem. Hopefully more (and a comment system) to come.
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Maybe I should change the name of this blog to "superkuh complains". Annoyance seems to be the only thing that can motivate me enough to post. This time around I'm annoyed at google search results being broken when I'm logged in to my google account. Searches for generic words like "vector" "surfboard" or "cat" will say they're showing x of 82,000,000 results. But if I go down to click to page 2 of results, then 3, then 4, the results run out. There are only 4 pages of results for the word "vector" and it starts reporting "~x of 381 results" instead of millions. The screenshot is a youtube link demonstrating the problem.
I didn't notice this myself. A friend on IRC was having the issue and asked if anyone else was. I thought he was just confused or bullshitting or something. But it happened to me too. I spent the next day asking around and 20 people responded. 7 of them had the problems of limited search results and 13 said google was behaving normally.
The only useful information I've been able to figure out is that it's account based. But if I am logged out and it's working and then I turn off javascript and get shunted to the mobile site the problem happens again. It doesn't matter what OS, which computer, browser, or IPv4 IP I use. So,
Bad Good Logged in with JS x Logged in no JS x Not logged with JS x Not logged no JS x
I sure hope it's just some bug and it gets fixed. I did submit a few "feedback" reports just in case someone cares. For now I'm keeping an extra browser open and logged in to google just for google services (like youtube) but it's tedious and I wish I didn't have to.
It's super weird.