In our Exchange 2013 environment, 80% of our servers have NetBIOS disabled in the NIC properties. To make our environment consistent, I wanted to disabled NetBIOS on the remaining servers. I searched to see if Exchange 2013 needs NetBIOS, and besides for disjoined namespaces, I couldnt find a good reason why I couldnt disabled NetBIOS across the board.

Correct, Exchange 2013 doesn't need NetBIOS besides for disjoined namespaces or if you have a member computer that is disjoint or if the NetBIOS name of your domain controller differs from a subdomain of its DNS domain name.  I think you're ok to disable across the board.

Good article below about Disjoint namespace scenarios:

https://technet.microsoft.com/en-us/library/bb676377(v=exchg.150).aspx