If we're going to have this kind of accuracy when it comes to demographics, it shouldn't just be baby booms.
It could also be argued that in societies where the military only covers a small fraction of the population, there's no baby boom, especially when there's also no real war economy.
That's why imo it doesn't make sense for Stellaris to have baby rooms: soldiers don't actually come back from war, our pops don't actually need to sacrifice anything in supporting the war effort. Most of the time, they just get more or less happy.
Additionally, I don't think peace needs this kind of passive, boring reward. By staying at peace, you're already not spending the ressources for war (like alloys to build more ships or energy to maintain those fleets).