Nonsense....the -400 and -800 have two overwing exits (on each side) so Boeing never proposed only having one each side for the 900. What redesign!?
Despite the fact that the 737-900 has over 9% more cabin space than the -800, it's still limited to the -800 maximum of 189 pax for evac purposes, because of only having the 2 exits.
If Boeing want to stuff 220 pax into the 900X, they'll have to add another (3rd) overwing exit. But they've recognised this....