I do think it's reasonable to expect a late check-out as elite, even if it is not guaranteed. It's how other chains typically do it, even if it doesn't work all the time...
the problems with Wyndham are that for one, usually staff isn't trained on elite benefits, so even if you ask for it, they don't know what to do.
An even more basic problem is the lack of integration between the corporate booking system and the property systems. I ask every time at check in and 9 out of 10 times the staff doesn't have.my rewards number and/or doesn't know/have my status information. That much marketed "blue band" of Wyndham Rewards is at best a dotted line, so don't expect a lot from the program. Bottom line, it's a rewards program with good reward rates, not a loyalty program with perks...