I understand your just tryin to help, but your info is slightly off. Your right T3 and T4 flanges differ, but the term T3/T4 turbo describes a specific turbo. Its called a hybrid because its one piece from two different turbos bolted togather to make one.
"The T3/T4 turbo is called a hybrid because it has the turbine housing of a Garrett T3, (the same turbo used on the 2.3L turbo Ford Mustangs), and the compressor housing of a Garrett T4. This combination of parts allows the T3/T4 to spool up quickly and while pumping a larger volume of air than a straight T3."
Heres a link with a small amount of info.
Changing to a bigger turbocharger
Just tryin to clear up a misunderstanding.