If you decide to follow it you probably should make sure everyone is well aware of it before asteroids start getting placed.
This rule is actually fairly common in many tabletop miniature games, like 40k, Flames of War, Warmachine ect... Both sides put the terrain on the table then one side gets to pick which side they use.
In most tournaments the terrain is set up before people start to play but still one person gets to pick a side. It helps keep people honest when placing terrain. It's kinda like when kids have to share a candy bar or something, one gets to cut the other gets to pick, so you know the one cutting will cut as close to the middle as possible.
That said in X-Wing for tournament play they decided to make the rock placement part of the game so it doesn't work the same here. Also rocks in X-Wing don't have quite the same impact that terrain can in other games, since they don't actually block LoS or anything.
That "keeping the field honest" is easiest reason for using it but like I say it is important for both sides to know how things are going to play out before they start.
Although all of the "terrain" was pre-printed on the maps I'm trying to remember how WotC did it with their DDM and SWM skirmish games. I believe it was one player got to pick which map to use but the other then got to pick which side, A or B, was "their" side of the battle.