That's not what
@RedHead0186 said at all. They just said that, contrary to what people on the internet say, the Wish class ships are not actually larger than the Dream class ships (obviously the Adventure is a different story). Many reports and comments on the trusty internet imply that the Wish is much larger, leading to comments about how the dining rooms are all smaller, etc. But it's not a larger ship.
They did not say you can’t have larger restaurants on a larger ship, they said that it isn’t a larger ship.
The Dream is 1115 feet long, the Wish is 1119 feet long.
The Dream is 137 feet wide, the Wish is 128 feet wide.
The Dream is 217 feet tall (14 decks), the Wish is 221 feet tall (15 decks).
The Dream has 1250 staterooms, the Wish has 1238 rooms.
Both list a passenger capacity of 4000 and about 1500 crew.
The Wish class ships are not particularly larger than the Dream class ships, which was all they said.
Could the space be used differently, for sure! Do the spaces feel a bit small and cramped, definitely. I don't think you'll get much argument on that. Would making them larger take away from something else, yes. Perhaps a smaller spa area or concierge area. Would guests then complain about that, yes.