Don't ask Freddie Roach about it! He calls it "playing boxing" and "pattycake"
I'm far from an expert, but in a sense I agree. In my opinion, it's more to train muscle memory and pattern recognition and less punching technique. Definitely not training for power, but possibly helps with accuracy, timing and hand eye coordination.
May can get away with it because he's already a great boxer. As a noob I think you'd be doing yourself a disservice training that way. The holder has a job to help reinforce good technique with the proper feedback on the pads, and playing "pattycake" when you can barely throw a proper punch with good body mechanics as it is seems ineffective.