Sure, you could put a 3 Ghz CPU in your microwave oven, or vacuum cleaner, or whatever. But now, your power consumption is significantly higher than your competitor's product. And you may now have problems with heat dissipation. And your BOM cost is a few dollars more. So yeah, in some kind of theoretical world with unlimited resources, performance is no longer a concern. But in the real world, it very much is.
The other dimension to performance is realtime guarantees, which Minix can't provide. So overall, I think AT is just whistling in the dark here.