Mounting nfs in DFly versus linux

[walt]

A little background first:  when I nfs-mount a read-only fs in linux,
'mount' will wrongly list the mount as read-write unless I specifically
use the '-o ro' flag when doing the mount.  Userland then fails when
attempting inappropriate writes to that read-only fs.

In DFly (I just noticed) 'mount' does not tell me whether a fs is
mounted rw or ro.

My question is:  is the whole mechanism different between the two
OS's for determining the write status of a mounted fs?

And for nfs in particular, does the nfs server tell the client
system about read-write status at mount-time -- i.e. is there
any reason that the read-write status should ever be ambiguous?

Thanks for any clues.