This may sound strange at first.
If you think about it, most analysts at BBs come from decent to very good schools and have stellar gpas along with high GMAT scores and 2-4 years of very good along with high paying i-Banking experience. We know these analyst positions are not easy to get.
So your thinking he has the grades from the great school, he has a high gmat and some great work experience so he should easily be able to get into a Top MBA program.
Unfortunately, there are a huge number of people that are also analysts at BB banks that have the same high gpas from good schools along with high gmat scores and the same analyst experience.
This makes it tougher for an i-Banking analyst to differentiate him/her self from the rest of the other analysts from BBs.
On the other hand, if one were to go into industry and have the same high gpa, high gmat score and 4 or so years of work experience in an accelerated program they would be competing with a much smaller peer group (those from the same position and industry). This would make it easier for them to stand out when compared to their peers.
This would make it easier for someone with non-IB experience that happened to have the high gpa, gmat and solid work experience get into a Top MBA program.