RFC: what should git rev-parse --flags HEAD do?

The documentation for git rev-parse --flags currently states:

    Do not output non-flag parameters.

Therefore, one might expect:
  $ git rev-parse --flags HEAD

to produce no output.

In fact, it outputs the sha1 hash of HEAD.

Can anyone see a reason why git rev-parse --flags should not be
modified to match the documentation?

If there is agreement that this should change, I can re-roll my
current rev-parse series to include such a change.

jon.