Not quite. They are simply different. Simply because they are RTS games made by the same company does not mean they should be the same. We give Relic hell (and they deserve some of it) but you can't argue that they have bright designers and they can come up with new game play ideas. Unless they decide to listen to Sega and mess with the game and sell factions as DLC (Chaos is a pre-order DLC in CA's Warhammer: Total War wich is ludicrous).
thematically yes, they're quite different. mechanically, coh, coh2, and dow2 are quite similar.
knockback and melee, and to some extent stuns, are also thematically appropriate to WWII, just slightly differently from 40k, and would add depth to the game.