A steady stream of accounts like yours of "it says my intake should be X, but when I ate X I added weight".

In your own case you've yourself proven that the sources you've found are wrong or at least have a ridiculous error margin, given that you've measured that your maintenance intake is much lower than your sources claim it should be.

Meanwhile it's exceedingly rare to see the opposite.

One of the big issues appears to be that people take advice based on a belief they are more active than they are. E.g. as I mentioned elsewhere, pretty much anyone in an office job is sedentary by default, even if they spend most of their spare time being active.

Personally, I tracked my calories for 6 months and found out whether I'm losing or gaining weight. I averaged 2700 and didn't appreciably gain or lose. I cut down to 1300 and started losing weight.