I think one problem with this is that a JNI solution would be "trivial" but is wholly unsatisfying (JNI being somewhat incompatible with the performance goals). The Unsafe and/or ByteBuffer solution on the other hand would be a lot of work to create and maintain (so much so that I wouldn't sign up for the job).

SBE on the other hand is targeting a space dominated by C++/Java/C#. They can basically ignore every other language binding without losing any of their target audience. It also doesn't hurt that they have a patron with a financial motivation to back them...