Never, but I have heard of it. It makes sense, as the rootstock will be well grown and large. Go for it, and report back next year. Someone on here must have tried it

Yes, been there, done that, roots rotted away when planted in Spring.

I do think runner beans are perennials so should regrow; would agree though that it is sensible in our climate to treat them a bit like dahlias so as to prevent rotting - probably wet, freezing ground that causes it.
I will try one year overwintering them in pots in a frost-free place.