It seems that zfs receive -F -u would mount a received filesystem after
receiving a full stream if a destination filesystem already existed (and, thus,
got destroyed and re-created) and was mounted.
How to reproduce:
$ zfs create rpool/sandbox
$ zfs create rpool/sandbox/from
$ zfs create rpool/sandbox/to
$ zfs snap rpool/sandbox/from@snap
$ zfs send rpool/sandbox/from@snap | zfs recv -v -F -u rpool/sandbox/to
receiving full stream of rpool/sandbox/from@snap into rpool/sandbox/to@snap
received 41.7KB stream in 1 seconds (41.7KB/sec)
$ zfs get mounted rpool/sandbox/to
NAME                  PROPERTY  VALUE    SOURCE
rpool/tmp/sandbox/to  mounted   yes      -
This behavior can be problematic if the mountpoint property changes either
because it had a non-inherited value or the stream contains properties because
it has been generated with either -R or -p.