This is the kind of situation where we're supposed to go with the flow
The actual Reversi ending is not important in the context of the story, only the fact that it was perceived as being excellent by the other characters.
It's hard enough to come up with a decent ending for a real manga. They could've left the Reversi ending off-panel entirely, but they did not, choosing instead to show something suitably epic whilst knowing full well that not every Bakuman reader will agree. If anything they at least deserve credit for having that much guts.
I actually liked the ending but disliked the execution - the last panel with them lying in the middle of the street lacked focus imho.