As the OP pointed out, one of the big differences is that Bill Gates never said "go out with me or I'll fire you", whereas McClure clearly indicated he was choosing between hiring and hitting on.

Who knows exactly what it was like for Bill ans Melinda. It isn't difficult to pick up on social cues of someone illustrating a mutual interest in you before you outwardly hit on them. It's also not difficult to respectfully ask them if they would like to get a drink, in a personal context. There's no evidence McClure did either.