Anyone got the 10.15 DP to open an encrypted Time Machine sparse bundle?

The 10.15 install produced a nice little flashing grey No symbol on its first boot as beta OSs are want to do.


But when I went to restore from Time Machine it seems the Migration Assistant can't read network shared, encrypted sparesbundles. It doesn't even prompt for the password, just says its empty.


File's fine if you boot into the OS and manually open it.


Anyone managed to convince the Migration Assistant to open one or am I copying things by hand?