Does seem strange - what happens when you want a mortage on a Seattle-price house? Do you tell them you only get paid £160k but you're definitely going to be getting a big bonus this year. Who would believe that?
Income is income in the US. Doesn’t matter if that income is monthly or one big check at the end of the year.
They look at what they can verify on your taxes. So let’s say you made $350k at Amazon last year, that’s all they really worry about. Doesn’t matter if only half of that was salary. They’d still consider your income as $350k and use that to approve whatever amount you’re looking to borrow.
If you just started at Amazon they wouldn’t be using your income to verify anyway. They’d want your previous work history going back, in some cases, 5 years.