Exactly. Some people have learned nothing from the last few years.
This could work, like AIM did with the Avengers, although I struggle to see the point since, unlike AIM, HFC doesn't do anything but throw S&M parties and plot to take over the world; any good they can do can be accomplished without them. But like I said, without Emma in the X-men, she'll get either sidelined- which happened after Secret Wars- or slide into villainy- which was the path that Marvel seemed happy to let her take in IvX and Secret Empire (with the trying to turn Tyke into Cyclops thing).
Also, often keeping the characters out of the X-men proper has consequences- see Colossus, Kitty and Nightcrawler being left out of TAS in favor of newcomers like Jubilee and Gambit. Emma wouldn't have appeared in WatXM cartoon if she wasn't a mainstay in the comics at that point either.