Freenas - Safe to delete legacy datasets?

So, I updated a Freenas box to 10.2 "Corral" and now I see a few system datasets which seem to be not needed anymore.

zfs list

tank                                                   3.58T  1.68T  11.6M  /mnt/tank
tank/.system                                           23.8M  1.68T  37.4K  legacy
tank/.system-a361886c                                   258M  1.68T   258M  /var/db/system
tank/.system/configs-f19d2a8de1c649400000077b09fd22e9   637K  1.68T   637K  legacy
tank/.system/cores                                      788K  1.68T   788K  legacy
tank/.system/rrd-f19d2a8de1c649400000077b09fd22e9      43.4K  1.68T  43.4K  legacy
tank/.system/samba4                                     305K  1.68T   305K  legacy
tank/.system/syslog-f19d2a8de1c649400000077b09fd22e9   22.1M  1.68T  22.1M  legacy

The "real" system dataset seems to be tank/.system-a361886c. Can I assume that it is safe to delete all datasets with a legacy mountpoint?

Edit: There is an answer on the Freenas Forums. Link. But it lacks detail and works for me is not a good explanation.