I know the question might sound silly, but my thought process is this:
If your ISP supports IPv6, and you use it from your PC all the way to them (i.e. PC → Router → Modem (if not router/modem comb) → ISP), there is no need for NAT (Network Address Translation).
If your modem/router are particularly weak in terms of hardware, it processing the needed steps for NAT could add latency in waiting on it to do it’s job.
I don’t know how intensive that process can be, but I do know ISP routers/modems can be pretty terrible at times. So that brings me to the title’s question.
Obviously you can’t affect things outside your network (i.e. other people not using IPv6).
I also wonder if IPv6 has different protocols that would lower the overhead on data transfer to also help with this. I don’t know much about it beyond some basics at the moment and am learning about it, and the original question came to mind, so I thought I’d ask it here.