2. It was already established in Apple v. Pepper that developers had standing to sue Apple over App Store policies. The case then went up to the Supreme Court which ruled that consumers also have standing to sue.
3. Showing consumer harm may help Epic win their suit. But it's not necessary to establish standing to bring the suit in the first place.
In any case it seems like the goalposts have been moved from "Epic needs to establish standing" to "Epic needs a strong case". My point was only to correct the former misconception which for some reason has been incorrectly repeated all over this thread.
Standing needs to be established separately for each claim, yes, but I expect in this case the $300 million in fees takes care of that across the board.