Agreed. Nobody is beyond temptation. The rule merely helps to create a "safe space" in which the marriage can flourish. Billy Graham had the same rule about being alone with women. It may be considered quaint or "square", but it's remarkably practical and creates an unbreakable bond between husband and wife. I strongly suspect that the wives (in both cases) follow(ed) the analogous rule.

It's probably a good question to ask a prospective marriage partner. If they are 100% into it, you found a keeper. If they laugh in your face, move on.