Homeworld created in empty sector

[Makinus]

Apparently when i use a Gas Giant/Hydrogen race, that in my mod only have Huge and Large planet types, it, even on Average, always start in a Large planet, and until now (around 10 tries) never tried to start in an empty sector (that i supposed would happen if the selected a mediu planet size)...

Would it be that, in Average, with different planet sizes for players, if the game can't find a medium planet it always select a large one? Or the repeated normal starts are only a probability fluke?