The tiers for our site are nothing to do with the official VGC meta
In VGC, any Pokemon can be used as long as it's not on the banlist
For our singles tiers, in OU, you can't use Pokemon in Ubers; in UU, you can't use Pokemon in OU and Ubers; in RU, you can't use Pokemon in UU, OU and Ubers, etc you get the idea