I think it is more detrimental as it stagnates the child brain into thinking magical nonsense is real which opens the door for further belief in nonsense and superstition.
Also, why would you not want your child to know that YOU were the one behind the gifts?
So when you're an adult, at least you have one innocent/magical/happy moment of your childhood ...
Nothing beats a Xmas morning when you're a kid ....NOTHING , and without Mr.Santa in the picture , the whole thing is fucked.
You grow in to a a sad soul individual looking for people's approval by being muscular...... sad.