KT is not mandatory btw. Even if you build all those buildings, you are reaping the rewards from them. Don't forget you have other choices of Armor and call ins aside from KT.
Not really? There are 3 call in tanks in the game for OKW, the PIV BG (Which nobody uses for obvious reasons), the Command Panther (which is excellent), and the Jadgtiger. But none of these fulfill the roll the KT does, and are more risky choices than the KT.
If you are fully teching typically it's because the game is drawing on long and you aren't shooting for a specific piece of armor. If I want a Panther ASAP I don't back tech before I get one. Because that's 40 fuel your not getting back.
Late game you won't be building Puma's, or Flak HT's, and the Battlegroup HQ isn't prized for it's units either, mostly just the reinforce point.
His point about it being defensive is right, it's the slowest of the 3 heavy MBT's, but is has the same armor as the IS2 now which is much faster than the KT which has only about 1 extra Jackson shot's worth of health more than the standard heavies.