Well I said CoDish cause many many arcade shooter maps tend to have no windows where you exactly would wish one and more often normal buildings would have windows.
The thing is simple. I'm playing a realism shooter, so I expect a realistic surrounding and battlefield. In war actually any window could "hide" a person behind it. Now, ingame you sort of handout a certain amount of windows, that on several occasions will leave you vulnerable with no sight on the enemy at all.
Opening up the second floor rooms will give more challenge to the Allied sniper to take care of this threat. If maps do not have the environment "necessary" for some roles, you actually do not need them at all.
Take a good look at Grain Elevator, there's windows on every floor that can be used to shoot at attacking Germans. So why shouldn't you be able to do the same as Germans on Commissars?
Maybe you remember the map Kharkov from the Mod days. It was an awful map, with two streets cut through the town and almost no place to take cover if the enemy tank approached. My problem with this map to this day was the inability to enter a building, get to a certain room and window and open fire on the enemy.
You need windows facing the enemy, otherwise you do not need to defend it at all. You need to be able to take out attacking infantry. Imagine Spartanovka church had all windows facing the Germans blocked! It's actually annoying too that none of the houses on the left/right front is accessible. Would give more challenge to the map. Same for Commissars. Smoke nades would need more responsible usage and this is the team's issue, not the map's one.