Actually it is a GT-R. The '2 dr', which is actually referred to
as a coupe, comes in GT, GT-T, 25GT and GT-R spec for the R34
Skyline. The 'GTS' is a specification only available on the R32 and
R33 models, through the GTS-T and GTS-M models for example.
This yellow R34 is indeed a GT-R. You can tell so by the stock
Brembo calipers (the twin piston example present in the rear of
this GT-R, as the owner has changed the front calipers to Stoptech
six piston if im not wrong), GT-R specific interior (including
bespoke bucket seats, wheel as well as console computer), the GT-R
specific forged rims, GT-R front grill, diffuser and rear spoiler
as visual ques.
So it is indeed a GT-R.