I assume that last "unless" would be the key: if the acquirer is overpaying for the company, as a way of transmuting what's really a hiring bonus into a capital gain, that could be problematic. But it seems like it'd require actually showing that there was overpayment, which courts tend to not want to get into except in really egregious cases (like politicians overpaying for houses as a way of funneling money somewhere), because of how difficult it is to objectively determine.