Fakhar himself admitted that he was injured, which is why he wasn't selected in Pakistan's recent ODI series. Do you know more about Fakhar's body than Fakhar himself? Kinda sus.
Keepers have a far more strenuous job than the average fielder, lol. This is why so many teams have keeping duties rotated between different players. That said, it is still a relatively comfortable way to spend half the game.
A batter, who has a much less strenuous job, getting injured repeatedly is completely unacceptable.