No disrespect intended, but this doesn't make much sense. You are saying that a planet that has a "raw" PQ of 8 can only be increased through game actions to 11, while one of PQ 1 can go to 19?
Yes, in Dark Avatar, that is how the terraforming techs eventually work out.
As I said, however, that is absolutely NOT the case in GC2:DL - In DL, low PQ planets are fairly trashy, although there are strategies that can use them quite effectively (as multiple tiny lab sites for example, since labs have no dependence on population or anything external except total civ finances).
Now, the base PQ8 (or 5, 6, 7, etc) planet in DA has a chance for tile bonus' (Precursor Mine, Fertile Ground, etc) that will never show up on a low base PQ planet, regardless of planet-forming improvements.
Note that various random events in either version can ramp up the PQ of ANY planet, doubling or quadupling the current available tiles in some cases...but you can't manage that, other than to do things (exploration, invasions) that stimulate random events.
drrider