As I suspected, there was a syntax error in my command, in particular with the '-delete' placement. It should always be at the end or will ignore the filter and assume deletion of everything. I find this pretty stupid, but it is what it is, I should have checked the small print. So I'm the stupid one.
Ironically, what seems really lost was my 'backup' share that I had setup. This was intended to be the source of a clone to my old decommissioned server, when that was brought online as a backup server later this week. I'm trying to restore this, as the array has not been overwritten.
Unfortunately, this happened first.
As it turns out, after more careful review, most of what is lost can be replaced or regenerated. The 'system' and 'appdata' is basically lost, and locked onto the cache drives in btrfs, which I'm trying to reconstruct. I noticed that all my VM and Docker configurations disappeared from the UI.
I'm reconstructing the cache drives, and trying to pull the file structure off it. I'm having some success using recovery tools.
ReclaiMe Pro and UFS Recovery seem to be doing pretty well so far, but we'll see.
Saying that, is there any way I can restore my docker settings using a backup (Meaning what I pull of)?
Also, for example in a normal backup/restore scenario, how do I backup/restore 'system' data and configuration?