I see your point, but...
most people use the tempest just as a 262. Thats becouse the tempest cant really do much more. In the other hand the jug can do the same, can come at high alt, BnZ like nothing else, get 10+ kills and escape uncatchable. Only a very few planes can catch it from co-energy, temp, dora, la7, 109k, but it takes a very long time.
But true, the tempests military-power speed is superior.