I think the correct way of analyzing this situation is to use bet/(bet+pot) and if you have more equity that the output of that formula it's a call.

I think it's because you're closing the action and are either calling or folding and not raising. So the decision ultimately boils down to your pot odds and your equity vs villains range. This is a similar situation to facing an all in, in a HU pot when your last to act with only two options; fold or call.

This may be incorrect though not 100% sure.