That's normal. With LXD 2.9 and the storage pool changes, LXD stopped generating automatic «root» devices for the containers, instead relying on inheritance from the default profile.
So in LXD < 2.9, every container had a local «root» device which you could then set properties directly on. With those LXD versions, adding a «root» device to your default profile would be entirely ignored as all containers would override it.
In LXD > 2.9, containers don't have any devices by default, they instead rely on inheritance. Meaning that if you want to override it, you have to add a new device to the container with the same name so that it overrides the one coming from the profiles.
«lxc config show NAME» vs "
lxc config show --expanded NAME" is pretty useful to see how this all works.