Your right to an extent, but for the record, not even half of scream is even related to Emo, it originated in Metal, which is where it most shines.
True it started mainly with Black Metal & Death Metal & still rains through with metal. But the difference between the metal screams from like for example Phil Anselmo(Pantera & Down) and the majority of "emo" (a term we're wearing out at this stage) singers is that in Pantera's music & most decent metal the screaming isn't being used to cover up lack of originality or talent. Gerard Way can't sing whatever way you look at it. Whenever the guy tries to hit a high note it sounds like a cat being murdered with a chainsaw with a blunt blade.
True, and nice example of Pantera, Killswitch Engage is another good Heavy Metal band for screaming.