By all accounts the Z8 is a carbon copy of the Z9 for AF and I know how the Z9 focuses. And no, its not as good as the R5. It has odd focus drops here and there. But in all honesty, its not that bad. However, there were areas where its better than Canon products. The Nikon combo I used, focused faster than my R5 and EF 500L II. So its not that simple. There's give and take. The AF issues were just not that big of a deal. If I were to say what's the best focusing cameras on the market, I'd rate them like this, R3 > A1 > R6 II > R5/R6/R7 > Z9. Never shot an A7R5, R8 or R10 so can't place them, however the difference from the worst on that list to the best, is very small. So small, that I wouldn't choose the camera based on AF alone. I could easily buy an R3... honestly tried hard to talk myself into it, but the bleeding tip of AF isn't everything. Even for a wildlife shooter where AF is the most important feature, if the performance is that close, other things come in to play.
You can definitely flaunt the fact that Canon is still ahead in AF, but just know you are largely splitting hairs. This is coming from someone who has bought only Canons for nearly 20 years.