bioctl's error message "Invalid metadata" for when you try to use a non-RAID disklabel partition is too unclear

[Tinker]

bioctl's error message "Invalid metadata" for when you try to use a 
non-RAID disklabel partition is too unclear.

Could easily spend a day not figuring out.
Kindly add something like " (is the disklabel partition not of type 
RAID?)" to that error message, as the user easily could think that 
"metadata" here would mean some structure within the particular 
partition intended to be utilized (e.g. "wd0a" etc.).

Thanks!