I'm not sure I'm ready to call hot side aeration a "boogeyman" like other homebrewers do, as I do detect an awful lot of minor aeration in most people's homebrews I've judged.
But I can't say where it comes from. Could it be HSA? Could it be a tiny bit of splashing while racking? Could it be from a little oxygen in the headspace in a bottle? Could be.
I am not ready to call HSA a myth, although I've had some instances myself where there was some aeration in the MLT and transfer and didn't experience any ill effects. I'd say to still be mindful that some experts have told us there is such a thing as HSA, so don't splash unnecessarily. But until someone comes forward and claims that HSA is a real risk and problem, I would also suggest not worrying about it much!