EDIT1: i changed min planet to 6, then custom galaxy with 6 planets 1v1, the game ended up with 5 planets, 3 asteroid planets and 1 dead asteroid planet... iirc that's 9 planets, not 6 , this game took me exactly 1:31, i was hoping for only 6 planets though, ima try 4 planet min, maybe i'll get what i want
EDIT2: tried 4 minimum, turned out to be 7 planets total, map was slightly unbalanced (one side had 4 easy planets, the other only 3), i think they would need to work on making decent small maps 4-8 planets total, anyway 1v1 hard comp, won in 00:59:20, that was straight caps, didn't build a single frigate save 1 flak to take the first planet, i've been building only caps simply because hard comps just pile on the frigates so i didn't want to bother matching them
apparently the system defines the planets as "planets not owned, or not designed to be owned"
i.e. not your home planet, and not the nice little asteroid behind it. I've run into the same problem.
the auto-map creator obviously wasn't designed to create strategically fair, aesthetically pleasing, or even accurate maps with a low planet number
yeah...
one suggestion would be to move all the planets closer to the star
you can mod that on your own.