For 20 fuel, its valid.
The cost is so severly crippling to teching and eventual armor.
Vet isnt that great anymore. 20 fuel however is a severe setback.
A single Maxim will deal with Vet infantry, as will they die just as fast to a mortar, as will a sniper vet even faster by depleting an even more expensive unit. Basically that Vet doesnt do jack shit for you except against infantry in a vacuum. It doesnt help you one bit vs anything else except small arms combat.
Yes, a single unit may be more effective, but at 20 fuel, its a bitter cost that bites you back, hard, as the game progresses.
I disagree (unless the soviet is the new soviet industry commander, in which case, I do agree). 20 fuel is very much worth it to gain map control. This is because there are very few things early game that can capitalize on fuel, meaning you can take a disproportionate amount of map control by buying vet3 grens and vet3 mortars. That map control translates to much more fuel income. ARMY NOW > MONEY SAVED because ARMY NOW is an investment that starts generating interest, so to speak.
I can give my personal experience against a player MUCH MUCH lower ranked than me abusing this. The guy was a terrible player but was able hold even map control by buying vet3 immediately when he had the fuel.