So pretty much the way I did it was so simple but it worked. I felt it worked better when my connection was straight trash. That means it's got more time to load the profile. So I got my main account loaded up in controller one, and well the second controller you click sign in to it and when it comes up who Is it? You click your account and quickly find a match, you have to spam in and out of cage match 4 times so it says to you "please wait" and if done in time you will get "fetching online profile" at a pretty similar time. Or if it doesn't try and do it quickly again as in cage match. The best way I could possibly explain it for Xbox 100% working though

Edit people with good connection will struggle with this as you need a shit connection so whilst doing this open up as many web browsers watch YouTube and everything to slow it down

Edit 2- I have done it this morning so it has worked again, there's literally such a low percentage of doing this near enough first time no matter how good you're at it. As well as when you fail make sure you log out of your second controller and retry.