It used to be, at least. Pretty sure. Does it still cause pops to decline? If so, that's a slow way to get rid of them.
Unrelated, but can you only build one non-habitat megastructure in a single system? I don't recall it ever being that way before, but I found out that I can't build the galactic assembly megastructure (or whatever it's called) "due to existing megastructure" in my home system. I built a science nexus there like 50 years prior and the galactic assembly must be built in your capital system, so I can't put it anywhere else. Really annoying that the one time I play an empire that has a use for it, this happens.
Admittedly, moving your capital system isn't as much of a headache in 2.2 since there aren't exclusive building upgrades for the capital planet like there used to be, but it's still a waste of like 200 influence to do it.
Also annoying that in the course of 250 in game years, I was never able to find an empire willing to federate with me for the achievement. Never got acceptance past -30 or so for anyone, and while I can't tell if that means the'd never accept the offer, I never got any to accept it with that level of acceptance.
Heh, except for the machine uprising in one of my protectorates, which finally triggered the league of unaligned nations against the war in heaven 30 years after the war started. I start to fight them to protect my protectorate, at which point the game decides that the new empire with over 20K fleet power is a valid choice for the league, and gives me a popup box asking if I want to admit them to the league. The machine uprising I'm currently at war with. I said no, since I'm pretty sure it wouldn't give me the achievement anyway and frustratingly still had to declare war on the awakened empires despite -500 opinion because by this point I had 1.3 million fleet power and they knew they couldn't beat me. I'm pretty sure they had no ships left either, since apparently fallen and awakened empires don't produce dark matter or zro, and so can't build new ships.