On my current playthrough was wardecced very early in game, had only colonized one world. The AI was a bit overpowered, and was bombarding my new colony while I tried to build up a fleet big enough to challenge him. He never invaded as I had built up a ton of defense armies, and he didn't have many transports yet. What I noticed, however, was pops were still migrating from my homeworld to the colony, only to get killed from bombardment. I was losing population faster than it could regrow, as my pops had the nomadic trait as well. I eventually just surrendered the colony so I would stop losing pops from my homeworld.
I think at the moment it does not make sense for migration to be active to a world that is being bombarded/blockaded.
I think at the moment it does not make sense for migration to be active to a world that is being bombarded/blockaded.