It's BS or ignorance. Neither Kiffin nor Carol runs any 4-3/3-4 hybrid. And Tampa 2 refers to the coverage, not the front. Like Carroll, Kiffin will mix up his coverages and play cover 1, 2 or 3 mixed in with man/press, man off or man under. Carroll is a Kiffin disciple and he runs the 4-3 under as his base (vs. Jimmy who ran the 4-3 over). This does not mean that Kifin will not change up and run different fronts/coverages, or is running a hybrid, it will just depend on the offensive alignment.
The 4-3 under creates most of the pass rush from the 5 tech (weakside DE) and the 3 tech DT. The 1 technique NT and the 5 technique (strongside DE) have gap control. The SAM will line up as a 9 tech to rush the passer if certain offensive sets present itself. The FS will line up over the split end (opposite the TE) more often than not. If 3 receivers (trips), the SS is called on to cover the slot/flanker while the SAM covers the TE. Unlike some schemes, corners would cover the wide receivers, even if lined up on same side. In 2 TE and 1 back sets, FS covers the 2nd TE (SAM covers the first) and SS plays center field.
Kiffin's (and Carroll's) underlying philosophy is to force the offense to the middle of the field, that the D needs to create turnovers and generate pressure with 4. Very simple.