Yes, the only downside with this method, is if you don't trust the other realm, and you think they'll just kidnap/execute your ruler. (Yes, this is a legitimate in game experience)
It is important to mention, especially when talking to newer players, that the "kidnap/execute" scenario is not something that is implemented in game mechanics. The other party can't just click a button that says "arrest the other guy". Arresting nobles is something that requires certain specific conditions, such as a war declaration, and even then there is no "arrest a noble" button. (Priests being a special case, and even then requires a war declaration.) And execution requires a certain set of pre-existing conditions. Meeting a foreign ruler to exchange regions, then arresting and executing them, is something that I have never seen happen, nor heard of it happening, in the past 6+ years. Any realm that actually pulled such a stunt would almost certainly find itself in a very bad spot with even their allies.
But I agree though too. The 2nd method is a terrible way to do things, but I've also seen it as one of the more common ones used.
It's the easy/fast/painless way of doing things. Blaming the players for doing it hardly seems useful.
