Again, the definition changes whenever blizzard feels like enforcing it, until then, its still just clever use of game mechanics.
Nothing else matters. You can't take one case and use it as predicant, because blizzard themselves are not consistent, at all, not even a little bit. Its an exploit when blizzard says so until then? Its only clever use of game mechanics, you dont have to like it... But thats the reality.
These are non issues and not question they ask themselves, its not the first time a similar scenario happens. If he sold them? They delete his gold and nothing else changes. They allow others to do it until they provide a hotfix for it or they don't. It's not as complicated as you want to believe, not even a little.
You would think so, right? But that's not how blizzard works and have worked over the past 20 years....
I'll repeat this for the 5th time now and maybe you'll get it...
It's only an exploit when blizzard says so and does something about it... Until then? IT FALLS UNDER CLEVER USE OF GAME MECHANICS.
Your personal opinion matters fuck all, only what blizzard thinks matters. And they are beyond inconsistent on these matters.