I have a question about seating availability on united's website.

I logged in to check alternative flight times and saw a good chunk of E+ availability on the desired flight. A co-worker of mine did the same and saw no available seats (E+ seats were blocked with the people icons, rather than typical shading). He doesn't have status, and is currently booked on a later flight in E-. Is there any reason he shouldn't be able to stand by on the earlier flight and pay the $14 to go E+? Any reason for the difference in views other than becuase I get free access to E+?

Any help would be appreciated.

Thanks,

Dan