UBRS and Scholo / Strat were not designed the same, however. The player cap to dungeons and raids were much, much bigger in early WoW.
Example:
http://puu.sh/fJ9tp/16c8e8f6d7.pngUBRS used to have a cap of 15 players. But later reduced to 10.
Scholo and Strat were designed differently, as its' evident by this:
http://puu.sh/fJ9A1/1e9f76a8b3.pngWhich used to have a cap of 10 players. But later reduced to 5. The same goes for BRD.
(A friendly reminder for the devs: Patch 1.4 introduced a ton of new rare items to Scholo and Strat as well as upgrading some uncommon ones to rare quality. And the entire tier drop system was changed to how we're all used to now. See:
http://puu.sh/fJ9Wx/e928c52d5b.png)
It's an obvious sign of design choices and difference. If you want to do Scholo and Strat 10-man. Then UBRS would be a 15-man. They're not both 10-man.