Idk about how BBitDW and BBitFS were added but there is no point to make a category on src if nobody actually runs it. From todays point of view 50 star and 8 star and probably even 80 star are all outdated (or could just be included in any%) but they have their own categories with certain rules because many people enjoy running within these rules. Without these runs there would be no point to have a category for 50 star or 8 star. However I don´t think src really matters to whether or not you can do runs of a category. If you find joy running "all bosses" then by all means run "all bosses" maybe it will catch on, maybe it won´t. : )

General rule of thumb for this game is: if people run a category it can get added. If something has no runs or very few runs it will probably not get added.