I'm hoping the 800V architecture at least leads to Tesla supercharger stations my Ioniq 5 can actually use after NACS takes over.

The current 400V architecture would charge even slower than the raw math would imply, because it requires the car to handle the voltage difference internally. Going through that path bottlenecks the charge rate at something Chevy-Boltish like 50kW that's simply not very viable for road trips.