GEP, let's not get our wires crossed; I agree totally with your key points, namely, the degree of risk. It is absolutely safer to land and swap over (because we're all much better (hopefully!) and have received more training in landing an aeroplane than changing seats in flight).
Without trying to antagonise the issue, and I'll firstly say that comparing this to landing wasn't the best example, I read your thoughts as following... Landing an aeroplane is nothing other than a phase of a planned flight. Why is not changing seats simply the same thing? Because you don't have to do it, right? But you have to land... (Unless you're the gents in the photo above, or one of those crazy meatbomber types!)
Ok then, at massive risk of thread drift, do you mind explaining why a large majority of pilots I come across take their aeroplane into the sky, and totally and needlessly roll it, loop it, spin it, stall it, put it on a knife edge then roll it some more?
There's nothing in the POH that prohibits it, so it's totally legal... But is it safe?
Of course, but only with proper briefing and training... Just like swapping seats in a PA28. I'd even go so far as to say, when taken right back to basics, the former is a hell of a lot more dangerous than the latter, given absolutely no training.
The crux of it is, no training is legally required to do either...