Hi dmatthew
I'm sorry but, as the Purchase Orders PRO add-on is quite new, we had no time to add full support to the Export PRO add-on yet. The actual version is 100% compatible with Purchase Orders (free module) but isn't able to read/write all the new features we added to the PO PRO version yet.
However, we are working on it, and will be available on one of the next versions 😉
Best Regards,
Salva.