It's called AD, and it's a thing he most certainly does have. Do the math, by the time he gets twice as strong, the next moment he'll be 4 times, 16 times, 64 times, etc. until he can just completely stomp cooler's AP.
He does have Accelerated Development, but you're exaggerating by how much stronger the accelerated development is making him. What makes you think he's eventually get dozens to hundreds of times stronger in moments? There's no proof of this, and Cosmic Garou never showed that level of advanced accelerated development.
You calling garou reaching a tier he has before in the same key as nlf has got to be the worst attempt at using the fallacy of all time. Meanwhile you are asserting that no matter how strong garou gets, cooler could just keep surpassing him. What a funny fellow.
He reached that tier because he'd copied Saitama. There's a reason that there are separate keys for Cosmic Garou and the Parallel Timeline Garou, cuz one is when he increased his power by copying Saitama, and the other is the one where he never got that chance because the future Saitama one-shotted him.
I believe it's possible that Garou could evolve to get stronger than the Meta-Coolers. I just don't believe he'll have that chance when so many of them are fighting against him. When they see how powerful he is and how quickly he evolves, they're going to realize they can't mess around with him and just try to kill him. And my point is that Garou's accelerated development and reactive evolution won't allow him to grow enough to fight so many opponents who can grow in power themselves. I mean Meta-Cooler's upgrades allowed him to go from fighting evenly with Super Saiyan Goku to easily overpowering him in less than a few minutes. If that happens with thousands of clones, no way Garou's gonna be able to withstand that.
I'm more inclined to disagree on some of Meta-Cooler's other wincons, such as his ability to copy the abilities and techniques of his opponents. I don't think there's enough evidence in the movie for that, and I always believed that Cooler already knew the Instant Transmission ability beforehand. Regardless, he doesn't really need those wincons here, cuz all he needs to do is have his clones fire multiple Supernovas, and the combined AP will obliterate Garou.
Another wincon that's not being mentioned is Meta-Cooler's greater maneuverability with his flight. Cosmic Garou doesn't have flight, and while he can push off the ground to simulate flight, I still think Meta-Cooler's flight gives him more options for attack, and can let him fire attacks more easily.
Meta-Cooler can also prepare his strongest attacks very quickly: even in his non-mechanical form, he created his Supernova in only a few seconds, admitting that he could channel energy much faster than Frieza could. The Meta-Coolers are upgraded versions of himself, so they'd naturally be able to prepare their strongest attacks just as quickly, if not quicker. So again, Garou would be obliterated by hundreds upon hundreds of Supernovas fired in seconds.