Okw used to be the biggest offender in "free" stuff. Medics repair station and point denail included with tech. No extra cost no upgrading needed just tech. Now of course the dont just get them. Usf crews medic and retreat point at least require micro and are quite vunerable so their is higher risk involved, this balances out the benefits mostly.
Something okw did not have to worry about mostly if at all.
Free might not be the right term for axis upgrades. But they do pretty much get a bargain. Its all included. You get your upgrade with natural tech, you will always get acces to them. It does not delay tech however slightly that may be. You also get abilities such as riflenade inc nade next to new units.
So the stg,s for volks not being as strong as 2 bars seems fair.
You can think of it another way, Allies can choose what they want to unlock and when.
To argue that Axis tech tree is superior because you buy "bundle" of stuff is simplistic to the point of begin dead wrong.