that was a random chance Leo because the shell got in the house but before that there were 3 or 4 different shots that bounced right off the house and did no damage to the occupants inside. I'll try to re-create it but the very fact that the shell bounced off the inside of the house is proof enough i thought.
It affects the game if it doesn't do any damage and EVERY shot bounces off the house, not every other but every shot i fired at that house bounced.
Not every shell is guaranteed to cause damage, though. StuHs, mortars and all sorts of weapons can hit buildings dead on, yet not cause any actual damage to the squad.