I've seen this too, and it's reasonably easy to do during online interviews - it only strengthens my belief that any interview where you're asked to give a formal definition of something or write one of the cookie-cutter questions is pointless.

You hit the nail on the head with opening a discussion, asking for opinions, and suchlike. That's the best way to gauge ability and experience.

Questions that provoke debate and are not searchable are the way.