It's also the sight used on the 6pdr (if you don't want to wait until you see the whites of their eyes
), so ground use against light armour is a reasonable assumption.
I'll also draw your attention to numerous comments made by the late George Blackburn regarding the extended use of light AA units being employed for 'pepperpot' shoots in the major assaults (they burned out barrels like they were going out of style). Those would have required a ground sight as well, methinks.