I have just re-checked my photographs of the area from when I surveyed in October.

I personally think it /ought/ to be landuse as it is man-made and not naturally occurring, and that is echoed by some discussions on the wiki and the rejected proposal of natural=shrubbery - https://wiki.openstreetmap.org/w/index.php?oldid=2130624

I would say that the wiki description for natural=shrubbery fits what we have here, although it has never been accepted as a proposal.

It was probably a mistake on my part to tag as landuse=shrubbery when natural=shrubbery is better documented, but as there is no consensus on the correct tagging yet I would be inclined to leave it for now.