The APSS says it's vacuum insulated too, but we'll have to see how well it works.

No. That doesn't change the fact that the metal has a higher specific heat capacity than plastic. The vacuum only makes it so that, once it's hot, it stays hot longer. That's not really useful here as it shouldn't be staying in the aeropress for that long, where it matters. It may actually make it worse, because you'll need thicker walls, and two of them, increasing the mass that you have to heat.

However, I think the "perfect" heat to brew with is slightly below boiling, so if you just use boiling water then the heat loss is probably fine. Still though, you're paying a premium for what is functionally a downgrade.