Say Nothing?

A couple of times, I saw a service desk associate (F 19) and the department supervisor (M 23) being "too close" in a quiet corner of the store. I've heard that he's being transferred to a different department, maybe he's training her, I don't know. It is odd that they choose to do the training on a computer near the back lumber door. In the late afternoon, that's a secluded area. (I'm in Millwork and often help out in lumber after most of the lumber guys have left. That's why I've seen them.)

By too close, I mean zero space between them. They weren't making out, but they clearly were more focused on each other than on the computer screen. I don't think she's being harassed, but it is inappropriate behavior and he's her boss.

I get along just fine with both of them and I will not make any trouble for them. I was thinking of telling them that if the wrong person saw them, all kinds of grief could result. But then I thought, they both know the rules, they've seen the videos, it's their business, their decision. I'm old enough to be their grandfather and they probably would not appreciate my interference. So I will say nothing. Right decision?