You completely missed the point.
He believes that DLC commanders are limiting default unit selection amount in any way.
All these games prove him wrong as they have similar/same number of units in them, yet they lack additional ones that commanders bring, therefore its lack of commander that limits the rooster.
I personally think that the DLC system does limit the default unit selection amount simply due to the fact that the developers are now able to cut out content in order to sell at a later date.
I would have agreed with you if only I had not seen COH 2 at launch.
Examples of units cut out to be sold at a later date:
KV-1 (TOW)
KV-2 (Campaign)
Tiger Ace (vet 3 tiger)
Assualt Grens (Grens with mp40, remodel of the mp40 panzergrens in TOW)
+among others etc.
If some of these could be used in the default tech tree, (excluding extremties like tiger ace) there would be no reason to cut out content. The only factor is, that they could resell the content in order to monetize it at a later date.
Either way, it's not the first time game companies have done it. But really, I've seen many threads at launch asking for something like a KV-1 to go into the default soviet tech trees with very little backlash.