They set the post-tax amount without knowing the exact pre-tax amount, so whatever the pre-tax amount is they will just pay it. Even if tax rate varies person b

They set the post-tax amount without knowing the exact pre-tax amount, so whatever the pre-tax amount is they will just pay it. Even if tax rate varies person by person there will not be a huge difference. I checked one of my offer letter (not from google) and the wording is like "an amount of $XXXXX grossed up for U.S taxes".