Don't get me wrong. I like USB OTG but I just have a hard time to imagine why this is important for enterprise. You still have no file manager and apps are still quite limited as to where to read/write data. One example MS demonstrated in Build 2014 is the enterprise MDM where they showed how to easily disable write to SD card functionality on WP
As for Google Nexus, it's just to demonstrate how the most popular mobile platform out there doesn't support OTG out of box either although Samsung always supports it on its phones.
And this probably is why the feature didn't make the cut for WP8.1 (not definitive but we will know for sure when Dev preview releases).
Personally, I like to see Miracast more than USB OTG. And it is still unclear which phone will definitely get Miracast support in 8.1 (there are mentions of 1520 but no definitive answer).