Ok, here goes:

I´m playing a small, 1 star, 20 planets game against 2 AIs at normal difficulty to try out the new beta2 patch

being attacked by both, the Korsul Armada and the Trade Coalition, I manage to stall the KorSuls at a chockepoint and fortify the planet. Then move my fleet towards the Trade Coalition. After neutralizing their main fleet, I attack their Homeworld and becaus all my sige frigates have bite the dust in the previous battle, it takes a while for my 5 capitals to finish the job. Finally, the last TC colonist dies and the planet is ripe for the taking.

I have with me an Akkan with colonisation ability, so I just wait for it to kick in.

And it does, just not as I expected, for the planet is colonized - for the Trade Coalition. There is NO enemy ship anywhere in the gravwell. I bomb the planet into oblivion again, and again, when my colonisation kicks in the planet is owned by the TC.

Now, perhaps I am missing something here and I need some special ability to colonize a former enemy homeworld, but to colonize it and immediately switch allegience, now this is a bit much to belive.
Those frozen settleres in the Akkan´s hold are in for some pretty touch questioning, I can tell you.