Yes, but it is kind of strange to field 'once de gala' and tell them to save energy - then he should have started with some squad-players instead!
The 3 points are not as important as Tuesdays match, but we lost momentum, and have a bad run right now, that is not good. I'm not really afraid of losing the league-title, our lead is still big enough with the few matches left. But a loss to Madrid should always be avoided - so if it truly was pure tactics to try to clinch to the draw at 1-1, then we could have used all our 3 subs right there. Then we truly could have saved energy for Tuesday, while it wouldn't matter if we won, drew or lost, as you claim.
Well, Lucho surely was in a dilemma. If it had been another opponent he would have fielded another squad. But Classico at home, the Cruyff thing...you can´t do that. So you rather field your best eleven and tell them "Boys, play it smart. Don´t overpower here. We´ve got 7 important weeks to go with our biggest challenge on Tuesday". This could be the point. But you never now. We just don´t know what was going on in Lucho´s mind. We can only guess. But in the end the next game will tell us the answer, it´s quite simple. If we see a team running on full gas on Tuesday for 90 minutes (like against Bayern last season) then it´s clear we saved energy. If not, well, I suppose we will be in big trouble.