Someone asked the same question yesterday.  I addressed it.  Basically it would have taken me an additional 2 hours to recompile and run my entire test suite, verify, sign, and upload the new wallet just to change the version number in the about page.  At which point, I would have needed to reevaluate a target block for the fork, and you have an endless cycle.  It's purely cosmetic as getinfo reports the correct version, and this can easily be fixed in a quick update later.  This was the least important issue that needed to be fixed, and was more urgent to get the update rolled out so that everyone would have time to update their wallets.

Basically: It wasn't overlooked, but there were more important things to address.  Let us deal with the issue at hand first.