I'm not certain if that's always the case. I may be wrong, but a few days ago I had playtested a game in trainer where I used steal on an AI's nightfall. I had plagued the AI's field of darkness monsters down to 1 hp. I assumed that because nightfall temporarily was "destroyed", that the darkness creatures would die, and then nightfall would appear on my side. This was not the case.
TL;DR version, I have no idea if stealing actually counts as a "destroy", or if it just SAYS that.