In general I certainly wouldn't disagree with this, it's what I was alluding to with general ideas that stick with you. But I'd call this a different thing than opening study. For instance one can get Benoni like structures in the King's Indian, Benko, English, Nimzo, and more! And so it's not really understanding the opening, but understanding how to play a certain structure that arises in many different openings.

And it has nothing to do with memorization. I mean you mentioned the b5 stuff against Bd3/h3/Nf3 setups. You might not be able to calculate the depth of what happens if white manages to hold onto his extra pawn, but you can certainly calculate to at least the point of 'okay, I'm getting my pawn back in most lines, disrupting his center, and getting my play going. if the one line where he holds onto it (Bxb5 stuff) then he's going to have a bit of difficulty castling, his pieces look disorganized, his extra pawn and b2 both look weak.' That's more than enough on general principles to go for the sac I think.