And why, exactly, would Tabata trashtalk Nomura? Tabata owes a lot to Nomura. Nomura himself is responsible for giving Tabata his first chance with directing Before Crisis, after which he moved on to direct Crisis Core (collaborating with Nomura again) and then got to develop Type-0 (another game with Nomura).
Very few of FFVsXIII's problems came from inside the project itself (other than the game being a huge project and huge projects always have their fair share of problems to solve even in best case scenarios) and were caused more by company-wide issues, which delayed the production of what would be a massive production in the first place. First SQEX had the Crystal Tools problems that forced the Versus team to create their own custom tools since CT was wholly inadequate for what they were aiming for, then FFXIII was in trouble so the FFVsXIII team had to help with that for ~a year, then FFXIV1.0 came out and was a huge clusterfuck that put the whole company into chaos for many years. All of these were completely unrelated to FFVsXIII's development, yet had a pretty big impact on how its development could even advance.
In comparison, after the FFVsXIII team had helped finish FFXIII, it only took a year for Nomura to have the January 2011 trailer to show (made by a relatively small team) and the game world was fully traversable in Fall 2011. So the project did advance at a pretty steady pace while in Nomura's care when they didn't have stuff bogging them down. The game just was so late in entering full production + problems with XIV were hogging development resources + in the end the game they were developing was somewhat constrained by the hardware they were working on + the murmur about next-gen consoles started around that time, so they made the decision to ditch the PS3 version, at which point it seems they brought in Tabata to head the "next-gen version", probably partly to force Nomura to focus on Kingdom Hearts III more than he could have if he was still directing FFXV at the busiest time of its development.