But you really have no guarantee about the quality of the backup i.e. whether - if you had to restore it - you would have a fully operational phone.
Unless you quiesce the phone properly, certain files that are in use at the time of the backup may be effectively corrupt on the backup. (The effect of that may range from none, through minor annoyance to serious.)
That’s why I use Jumpdrive to do a backup of the entire eMMC drive. Yes, that means taking an outage on the phone. (For me the outage is under 10 minutes but I expect it would take longer the more crap you have on the eMMC drive.)