If they did that after the person turned down other job offers and possibly incurred explicit financial expenses in reliance on Google accepting the redlined changes - assuming they highlighted the changes when they provided them instead of trying to sneak it past - Google could possibly be liable for damages caused by that reliance if they were to be sued or arbitrated against.

It says really bad things about the corporatist labor culture in the US that Google doesn't have any reason to fear that type of lawsuit in practice. (I.e., they could make it too expensive to win, they'd still hire without a problem going forward, and the person who sued them would have trouble getting jobs even if they win.)