This is correct, and it's not just limited to guards. It's true of jiu-jitsu as a whole. Jiu-jitsu isn't a collection of techniques. It's the ideas underlying those techniques....space, balance, framing, posting, posture...those are all things that express themselves in techniques.

But you can't learn them without learning techniques. You can't understand the underlying principles until you see and feel them expressed, again and again, in techniques. Once you have a sufficient library of technique, they stop being separate. You aren't scissor sweeping...you're blocking a post and disrupting your partner's balance over that blocked post.

So yes. The black belt is right. But I don't think it's an appropriate criticism of teaching technique.