F4 x2 isn't recommended for the same reason 2 x6 isn't recommended. It's even worse in this case because it is in the beginning of the combo.
I think what playpal is saying is that you can't hit confirm it. I would say that it is possible to hit confirm actually if the JIP hits, yet is it impossible to hit confirm if the JIP is blocked then the F4 overhead hits because the person has the reactions of an 80-year-old woman and didn't block the overhead.
Getting a jump in punch on someone completely in the corner is very situational. For reasons stated above this wouldn't be able to be used reliably without hit confirmed it off a JIP. Another issue that adds to this not being a BnB is the high startup makes the timing awkward and somewhat strict.
I think what playpal is saying is that you can't hit confirm it. I would say that it is possible to hit confirm actually if the JIP hits, yet is it impossible to hit confirm if the JIP is blocked then the F4 overhead hits because the person has the reactions of an 80-year-old woman and didn't block the overhead.
Getting a jump in punch on someone completely in the corner is very situational. For reasons stated above this wouldn't be able to be used reliably without hit confirmed it off a JIP. Another issue that adds to this not being a BnB is the high startup makes the timing awkward and somewhat strict.