Why on earth would URF be disabled in customs?

It really makes no sense to me that URF would be disabled in customs simply because there is a bug that made players able to create a none random URF game. I love that URF is random this time to avoid people spamming the same champs every single game, but it makes literally NO SENSE to keep it that way in customs. If you want it to be random in customs you can just chose that option, or use the random function. Some players (including me) played URF customs because we wanted to try a specifik matchup for fun. We wont be able to do this now :/ The entire point behind customs is that you can play the way you want to, with friends or randoms players, and with as many people as you want on both teams (up to 5 obviously), no matter the ranks. Now we dont have an option to play URF in customs at all. This really screws some of us, and i wish that we would be able to have custom settings in a custom, rather than just shutting down the whole thing.

Tl;Dr I dont know why being able to chose your champion in customs is treated as a bug when that should be an option by default.