One wonders, given that they have over 300 737-800s in their fleet, what exactly there is that needs evaluating regarding the -700.
If they'd asked me, I'd have told them for free that it doesn't hold as many.
One story I've heard is that Boeing are supporting / sponsoring the aircraft in some way, so that RYR can evaluate the type. If true, I guess RYR can see a potential for the -700 somewhere.