What would be the problem if I chose to invade with 200 tigers instead of 400 pz3s? If that's the game I want to play why would the devs prohibit that? I love historical accuracy, but I also love what if alternate history scenarios... Even ridiculous ones.
Well, to push it a bit further, what if you had nukes in poland?
Its easy to mod how small the ahead-of-time penalty is anyway if thats what you want to do, but it would break the game too much to allow it as a supported option.