Is BBLAYERS_NON_REMOVABLE obsolette?

[Alexander A. Filippov]

It seems to me BBLAYERS_NON_REMOVABLE is obsolete.
At least I haven't found where is it used.

Yocto documentation said that was used by the Hob
  https://www.yoctoproject.org/docs/1.5.2/ref-manual/ref-manual.html#var-BBLAYERS_NON_REMOVABLE
that removed since yocto-2.1.
  https://www.yoctoproject.org/tools-resources/projects/hob

Likely it's time to remove this variable.
As I can see it's copied to all layers and assume it's just copy-past.

What do you think?