I like backstories in characters, and sometimes the writers develop one for their own use, and sometimes characters just collect random factoids which become a backstory. That's how most of Kirk's backstory came together. Sisko's apparently came together in much the same way.
Also sometimes writers (script and book) absolutely disregard previously established facts in lieu of their own 'story' :-\.
Hmm, I hadn't realized that they were at the academy at seemingly the same time. That just doesn't seem right, although, I suppose it is note worthy that Riker went out of his way to make a name for himself while LaForge apparently didn't. No doubt his actions on the Pegasus (for better or for worse) led towards Riker getting recognition. In light of Riker and LaForge graduating in the same year, that actually DOES suggest Riker probably benefited from that event a lot more then he'd like to admit.
I should also suggest where Sisko is involved (since this thread IS about him), he entered the Academy in 2250. He apparently ALSO made some effort to stand out too (compared to LaForge) considering he was a commander by the time DS9 was established and also apparently even a chief engineer long before LaForge was even in a gold uniform.
Bah, LaForge's history really needs some reconciliation. It sounds like he got screwed some where in his career where he essentially hit a full stop for reasons unknown.