Well, no, it isn't required. I just asked for him to add that in there so I wouldn't get loads of reports for it >_< But sure, you're more then welcome to make a multi-generation challenge in PG, just make sure it follows the other rules in there :3
I'd like to create a multi-generation Monotype Challenge thread in Pokemon General. And seeing as the only other challenge I see in there so far says "Approved by Aegis," I'm assuming that may be required. So, is this the case?