Oh they are, no question (allegedly, hehe). They would not be where they are today and in 2018 (where the charges end for now) without external funding.
The PL does have to prove it though.
And I think Kay's point is that the idea of financial cheating is more abstract than directly doping players on the pitch; I know the comparison is hated on here but United and Chelsea should be much, much better if it was only about money, and that there is a level of sporting competence that they've built (enabled by that money) that is distinct, according to Kay, from the money. It's no wonder that Sir Jim poached Omar from them and is trying to replicate their structure on this end.
Now of course, it's personal choice whether you choose to separate the two or not, when it comes to City.