I'm not sure the RS UK post is accurate. IFAB set the laws, they don't have any day to day operational management of them. I read it more that FIFA are fed up of individual associations tweaking the VAR rules and guidelines, and by that I of course mean the Premier League. So FIFA will play hard ball and say you either operate it this way or you don't operate it all all, which seems perfectly fine to me. IFAB will still define laws, including those related to VAR, FIFA will just take a more active role in policing its use.
And after tonight, where the PL have come out and said that VAR decisions in all three games were incorrect, they don't really have a leg to stand on.