After creating a new btrfs raid1 and was surprised to be greeted with
the warning

WARNING: Multiple block group profiles detected, see 'man btrfs(5)'.
WARNING:   Metadata: single, raid1

I asked on the IRC, and darkling directed me to the mailing list
suspecting this was a regression.
I am on 5.14.8-gentoo-dist with btrfs-progs v5.14.1

I have attached a script to reproduce this with temporary images/loop devices,
Along with the full output I received when running the script.

A shortened version of the commands that I ran on my *real drives* and
the relevant output is also provided below for convenience. P at the
end of the device path was inserted incase sleepy joe copies it
thinking its the reproduction script:

# mkfs.btrfs --force -R free-space-tree -L BtrfsRaid1Test -d raid1 -m
raid1 /dev/sdaP /dev/sdbP; mount /dev/sda /mnt/tmp; btrfs filesystem
df /mnt/tmp
btrfs-progs v5.14.1
....truncated....
....truncated....
Data, RAID1: total=1.00GiB, used=0.00B
System, RAID1: total=8.00MiB, used=16.00KiB
Metadata, RAID1: total=1.00GiB, used=176.00KiB
Metadata, single: total=8.00MiB, used=0.00B
GlobalReserve, single: total=3.25MiB, used=0.00B
WARNING: Multiple block group profiles detected, see 'man btrfs(5)'.
WARNING:   Metadata: single, raid1