I don't think that's true in most situations. I think most companies would still pay a severance out of a general effort to smooth things over, and some sense of social loyalties.

And some aspects of the agreement would be fine. No spilling actual business relevant secrets, nothing that would count as libel or slander, etc.

Nope, they'd have security show you the door and maybe threaten to sue you into the ground if you talk. They choose mkney because money is easier, but if you take this option away, you just get the stick and no carrot.

You think a business pays money out of a sense of "social loyalty"?

Companies don't need to offer severance to prevent ex employees from spilling business secrets, doing so is a criminal offense.

Part of smoothing things over is implicit of explicit understanding that employee also smooths things over that is shut up after receiving the bribe.