From a theoretical standpoint, you don't need to worry about that. You can conceive of metal hydrides or other forms of dense hydrogen storage. Even as LH₂, you're still looking at around 2700 Wh/L of energy. That's well beyond any known rechargeable battery.

And the "special alloys" really just mean certain types of steel alloy, and "nonmetal materials" really mean certain types of plastics. This is not a big challenge.

You still need very low temperatures and exotic materials for superconducting cables. Not to mention the power generation needed to sustain that level of power draw. This is a long-term problem that we're nowhere near solving.

As I said before, this is not a race and there is no finish line. There's nothing stopping fuel cell cars from displacing EVs at an arbitrary point in the future.