Yes, absolutely. This is a huge branch of competitive Pokemon we'd be blocking out if we'd not allowed this. This rule that covers unofficial content is there is block unofficial ROM hack games in particular; as brought up in the comments, the rules state:
Only questions about official Pokemon games are allowed. There are hundreds of different unofficial games that come and go all the time and have many varying rules; we can't cater to them all. Go and ask on their forums if you have a problem. Two exceptions are Pokemon Online and Pokemon Showdown which are popular battler simulators. But avoid technical non-Pokemon questions like why your internet isn't working.
Smogon rules and Pokemon Showdown aren't official, but they're such an integral part of competitive Pokemon now that they might as well be. There's easily enough online resources to cater for them and definitely have a large audience as well, and questions like the one you mentioned can be answered objectively. So they fit just fine.
