At best, you can claim misleading advertising (which, is often handled by the fair trade commission or something similar, and often has to show damages before they can award anything).
Does that cookie get read by Google? Of course, or there would be no point. Does it enhance their tracking? Most likely. Is there a GDPR compliant opt-out without loss of features? At first glance it seems not.
I'm glad the GDPR is in effect, so instead of "this should be illegal" we can say "of course this is blatantly illegal".
I hope they get a fine for this, with multipliers for how deliberate it is, and for keeping on defending the behaviour even after being called out.
This illegal things needs to be stopped it is not enough that only the people that understand it stop using Chrome.
If you can answer that question, and then suggest a possibility for them to actually lose that much market share, then you may be able to demonstrate that losing the market share is far more impactful than any currently possible fines.