I'd venture it's real. When one gets fine-tuned as when playing a musical instrument small changes in the action or tone are noticable to the player almost immediately. 2.25 lbs is what, a kilo almost? That's a significant amount of weight in cycling terms. Especially when trying to climb a 25% grade.

Of course higher grade bearings, drivetrain, etc. contribute as well. And maybe you're in better shape than you were last year?