One main arguement against the ISTP theory is that ISTPs are quite neutral whereas eminem is never neutral! hes anything but neutral!
Also can I point out that when eminem discusses his feelings he seems extremely confused and overwhelmed by them like an unhealthy Fi, like a tertinary Fi.
Also his Se is clearly not developed at all even if he uses it. At times he seems to rip the piss out of the Se nature of rap in a very Ni way. Like his Ni is ripping the piss out of Se!