To me, they're lying to push a narrative. No one's turning down a payrise because of that. Only stupid people who have never been offered that kind of money would ever make that kind of claim. So, I agree They're idiots. Just in a slightly different way.

It does depend a bit. The tax brackets are nonsense of course, but there are countries with allowance systems that don't fully decrease to zero as your income rises and at some point end in a hard cap. In those cases a raise might end up costing you due to losing the last part of an allowance.

But that never withheld me from accepting a raise, you're going to have to push pass that threshold at some point anyway.