I'm just guessing here, but it would be the type of deviousness worthy of AF.
Since SRPT was controversially approved based on a surrogate outcome, there is a chance that the post-market trials the company is obligated to run end up failing. In the case of this MRK news, AF may be making a list of people / goading people into arguing that the pembro approval based on the surrogate should not be revoked based on this survival outcome.
If / when the time comes that SRPT's follow-on trials show little effect, AF may start calling people out for advocating eteplirsen withdrawal when they looked the other way for pembro in SCCHN.
I think it's very much apples and oranges, given the preponderance of data validating the activity of pembro as a drug. But it's a typical twitter-type long term argument.