The guidelines have been followed as best they can, and had Nomura planned things better, this wouldn't have happened in the first place. He hadn't developed a home console game in over a generation, and while that's largely the fault of Square Enix, it doesn't mean you plan for something that could take upwards of ten years to complete.
Big budget games are expensive, and the reality of modern development presents some very different challenges (that he's in the process of learning with FF7 right now). That he was allowed to run away with his "vision" reflects poorly on Square Enix since they never should've let him in the first place, but it also reflects poorly on him as a designer for not knowing his limits. You don't have an unlimited budget to do with as you please, and the company doesn't owe you one either.
Some fans just have a romanticized version of Versus when they barely saw anything of the greater game in the first place. There was enough there to give you an idea, but that's about it. That's why you end up with nebulous descriptors such as "the feel of things" and "the tone of things" where most of what they saw was pretty insignificant, and they've let their imaginations run wild with it all due to some good trailers and some brief explanations. Nomura is good at selling a concept, and that's largely what he did, but the reality of executing a concept means you can end up with quite a different result. Since it was his vision in the first place, the more passionate fans have a difficult time letting go of things, when if he was the one having to present changes, it likely wouldn't result in this kind of scrutiny.
Asking Tabata to follow guidelines or consult Nomura is also insulting since he's the one spending years of his life bringing the current game to life. Their team has been pretty straightforward about keeping as much as possible of the original plan in the new game, and it's pretty evident they've kept quite a fair amount, but this isn't Versus XIII. It's Final Fantasy XV, and they course corrected they way they feel is appropriate.
The martyring of Nomura is frankly stupid. He's about to take four years to deliver part one of a game that's going to end up less ambitious than another project that he was taken off which received a messier four years, in part thanks to him. There'll be plenty of opportunity to crucify Tabata if he delivers a less than stellar product, but at least those complaints will have merit.