Managed file transfer is a real enterprise category with compliance requirements and serious budgets, dominated by proprietary tools. An open alternative would find an audience, and the .org is where such a project would live. FTP is one of the oldest protocols still in daily use, and file transfer as a problem has outlived it several times over. FTPX reads as the next thing after it, with the X suffix signalling extension or successor without claiming to be a specific standard.