correct
Even if tax on salary over a certain point was 99.9% the more gross pay you earned, the more net pay you would get.
It might not be worth the bother to some people, but you always end up with extra cash at the end of the month unless there is a rate over 100% or there's some system of fines.
What does happen in the real world, is people maximise their net hourly rate earnings. Once they get to a threshold where that begins to dip, they get other soft incentives. A better car, softer core hours, access to the executive washroom, subsidised Director's bar every Friday and tickets to that show everyone wants to see...