In assuring my 'gonna make it' target range to get to Select Executive for the first time ever, I changed my reservation from tomorrows' 148 NYP-WNL to 2172/412, choosing first class for the extra 50% points (regular and TQPs). After discovering that the 'change reservation' routine 'enter payment' screen, (why couldn't they simply have a 'use same credit card as original reservation option?), finding it very frustrating having to 'next' my way through all the CC billing info, I was surprised there was NOT a 'choose your seat' popup!! Maybe doing it on my Android phone is a problem? I even went back to the changed reservation, clicked on the 'modify' for train 2172 and it only took me to 'change departure', etc. No thanks! I'm not going to risk getting charged an extra $141 for the upgrade from 148 business class.
Maybe it'll let me choose a seat tomorrow....