When I research Xeno Ethics and choose Neutral, PQ for existing planets is instantly upgraded and any other planet colonised from then on have increased PQ as soon as I colonise. However if I gain another planet from another race the PQ sometimes reports incorrectly. Sometimes there will be extra green tiles available,other times the the planet will be a number of tiles short of what is being reported (ie the game will report the planet having a PQ of 17 when only 14 total tiles are present)