I was wondering about this too. I don't think I remember ever seeing anything below a class 4 in DL, maybe a 3 but there seems to be a lot of really low class planets in DA. I was wondering if it was by design to make the planet improvement techs more powerful, or if DA is just accidently generating that many sub 3 planets.
On another note I haven't seen any differences after researching the advanced version of a colonization tech. I though from the description in game(+50% colonization) that it would allow 50% more tiles, which would also offset all the really low PQs. After researching them though, No new tiles and no boosts of any kind I can tell(not in planet details atleast).
One last thing since I'm posting here might as well get it all out.

Currently there seems to be no way to tell foreign influence levels on asteroid mines until its in the process of rebelling, then it always says(to the right of the name) foreign influence is 9999.00. I realize that though may just be something that isn't full implemented yet.
another last thing(it really is this time

) I saw it mentioned you can now leave orbit in any direction you want, but I have yet to find a way to do this.
Thanks for listening. Any help to my confusion above is greatly appreciated.