Well I personally haven't been following Nomura's career as a developer, so I haven't followed every single interview he's done in his lifetime and can't really comment in that respect. But I haven't really seen anything translating over to his works he's had a hand in developing (beyond the role of a character designer) that's indicates he's full of sh** (I've personally found all works quite enjoyable).
Being full of shit (which I admit, was hyperbole) refers specifically to what he says about what he works on, not how he performs when he makes stuff, so I'm not sure why your focus is on that.
Nomura has a track-record of saying this that directly conflict with other people he works with, and that has been going on since the release of the original FF7 where he in interviews inflates his involvement in scenario writing, whilst everyone else relegates him to character design, and contributing to the development of the limit break system.
It carries on across on almost every consecutive title he's been involved in.
Add that to the fact that he is really vain as a person, and how he feels the need to constantly say stuff like "I didn't know this or that, and just kinda walked into it" in relation to his development work on several titles, which, in Japan, a country that general puts high stock in hard work and being prepared for things beforehand, comes off as extremely arrogant and narcissistic.
I really just can't stomach the guy, and never could ever since I met the dude for the first time at an local event back in the late in the mid 00's.
This shouldn't be much of an issue, but in terms of using him as source of information for speculating about the nature of the remake it is. Basically, he's not the first person we should be listening to about what's going on behind the scenes.
Also the main reason why I am incline to give the benefit of the doubt is that Nomura and Kitase's answers/statements were literally given in the same interview while together. If either of them thought the other was explicitly contradicting them on something, I think they would have least indicated that somehow. Since they didn't, I am inclined to believe that they were referring to different specific things.
Firstly, no they wouldn't - not obviously to most foreign eyes at least. They're Japanese, and they work for a large Japanese company. They're not going to air person disagreements in public, at least not to any meaningful degree.
Secondly, it kinda was a tiny clash there, since the emphasis of Nomura, when he followed Kitase's statement about overriding him on the character design, went on to say something that would translate roughly "I did specify that I would do this from the very beginning" with the "n" particle strapped at the end of the verb to denote an unspoken implication, which I would definitely take to mean "so, it's not true that I suddenly came out of nowhere in making this change - just saying".
Now, if you ask me which one of Kitase and Nomura is more believable, I'd have to go with Kitase here.
EDIT:
Ah and I just remembered (unrelated to the "model"/"CG data" issue) that AC/C did also feature Barret in his OG design as well briefly (during the opening sequence).
Perhaps this is what Kitase's "visual style of FFVII Advent Children" statement might have also been referring to. Because the above is significantly different from Barret's remake design, even beyond the lack of shades.
I don't think that point makes much of a difference though, since regardless of which of the two Barret models from AC Kitase was thinking of, both were rejected in favor of the redesign, and there is no reason why one of them should be incompatible with modern software/hardware and the other not.
And from a pure development perspective - there really is no reason what so ever, if they still have the original model files, and they weren't made in some completely obscure file-format, that they shouldn't be able to port them over to a new system.
I don't even see why he bothers. Why not just say - "well, I don't like the old models that much anymore and wanted to try something new"?