Although it does happen occasionally, its very very unlikely you would have a CW aircraft.

I would not make a buying decision based on a seat map.

I have had a mid haul A321 seat map for weeks on a GLA-LHR then when we boarded it was a regular SH A320

last week when I checked in 24 hours before my LHR-GLA I was in an exit row on a A321. when we boarded I was still in 9K but again switch to a 320 so lost me exit row.