I think the max charge rate for an Ioniq 5 is actually more like 225kW. The bit about 350kW stations enabling the 15m 20->80 charging is because the next step down in an EA/Chargepoint station is 150kW. And in practice, mine rarely gets up anywhere near max charge rate, though that probably has more to do with EA's station quality than the car itself.

The bigger issue with Supercharger is the voltage, if it's not a 800V charger. The internal converter in the E-GMP platform for a 400V source ends up being a limiting factor and drags the system down to something like 75kW, similar to a Bolt.