This game got even odder, but I have a theory now.
First, the other planet in my own system had 14 open tiles, and 9 of them were bonus tiles:
- 700% Manufacturing
- 300% Manufacturing
- 100% Manufacturing
- 100% Research
- 100% Morale
- 100% Influence
- Three 100% Farming
My theory is that the number of bonus tiles is affected by the galaxy size and the number of planets and the bonus tiles are distributed among the habitable planets. The game settings were all Random and the galaxy appears to be the largest one and there are LOTS of stars and all seem to have planets.
BUT!
I have not found any habitable planets outside my own system and I have checked at least 20 systems so far.
So, I think the bonus tiles are crammed into whatever habitable planets there are, and there may be NONE outside homeworld systems. If there is only one major AI and no minor AIs, then there may be only FOUR planets for all the bonus tiles that are supposed to be spread out in a gigantic galaxy!