Bullshit. It's like saying protein powder doesn't increase muscle on Ronnie Coleman or Arnold or anyone who is at their protein limit.
Some people have high creatine by themselves from meat sources or from own body, or some already have muscles saturated with it.
Creatine slightly boosts pure lean muscle growth. But most importantly it saturated muscle with creatine and increases its mass, ofcourse the increase isn't muscle tissue but water and resources bond to it. People usually count sarcoplasmic hypertrophy from glycogen as "muscle gains" even when they are short term and goes away after low carbs or depletion. Also as with anything when you stop doing it, it will go away. Also muscles are mostly water (75-80%), Mike Menzter also said that which reminded me.
Who will benefit from creatine? The ones who has it low. How can it help? Allows to push harder, allows to store more fluid and hydrate cells internally, may trigger MPS more often/recovers better.
It is like, "by itself" creatine don't go and build muscle, but it boosts whatever mechanism if they weren't already.
Some reality checks, don't expect signifiant size, don't expect significant contractile muscle size increase, expect water weight and boosted performance, but that is if only your muscles weren't actually saturated with creatine.
Ps: not sure about the boosted MPS signalling.