So I colonised a planet with titanic life on it, and got the 'Study or Ignore?' popup, and chose study. Apparently my researchers kicked one of them on the toe or something, because they got mad and took over my colony. I sent over some troops to take it back, and noticed that the fortifications were still partly up - and that the titans were benefiting from the bonus. I brought a fleet over to take down the fortifications, and they refused to fire on the planet, I assume because it's still mine.
I'm not sure which is the bug, but I assume enormous aliens shouldn't be able to hide behind human-size fortifications. I found this picture which illustrates my point:
The save is here:
https://www.dropbox.com/s/k5e0hxafrlw1n50/ironman.sav?dl=0
I'm not sure which is the bug, but I assume enormous aliens shouldn't be able to hide behind human-size fortifications. I found this picture which illustrates my point:

The save is here:
https://www.dropbox.com/s/k5e0hxafrlw1n50/ironman.sav?dl=0