VTY option "two-phase-access" is misleading
the option "two-phase-access" doesn't "enable" the MS to use two-phase-access, but actually forces it to do 2phase even if it requrested 1phase.
Hence, the VTY command should contain the name "force" in it, ie force-two-phase-access.
We could even change the VTY command to be two-phase-access (forbid|allow|enforce). This would allow also forcing MS to always do 1phase access (mostly useful for testing purposes or if a bug in 2phase is found).