It means they are randomly generated shapes based on a seed. And or that number of planets, the seed is random too. The real work behind this went into the planet generator.
The article you linked even explains it.
Last time I checked, anything we've observed is accurate in the game, and the rest is
procedurally generated beyond that. There's a difference between random generation (using entropy such as time or other noise, to calculate what should be what), and procedural generation (a seed, in this case the known universe, and the rest is generated beyond that)
Yes, a lot of the game is being generated. However, due to the nature of the game, everyone is going to see the same results, with only one random factor. Your starting position.
Unless something has drastically changed since I last researched this game.