Vickers .303 MMG ordinarily feeds from the right side,and nothing in the manuals I have mentions anything about the feedblock being reversible. Thinking back about working on a Vickers, the direction of feed is not reversible - it would require a different feed block (at least) to feed in the opposite direction. For a live demo, ...
See
https://www.youtube.com/watch?v=hPv_f_aSyP4
However, the used cloth belt needs to drop into something akin to an ammo box in a tank turret - cannot have them 'dribbling' onto the floor and jambing things up. This leaves the question: where was the .303 inch belt box with the live ammunition, assuming the Vickers used was fed from the right as per normal? Maybe under the .50 cal Vickers gun adjacent?
If you look at the AWM image of the RYPA being used, it shows an angled ammunition box support on the right side of the 'turret', which I assume is the same as in the tank. This would seem to be the support for the .50 inch Vickers Short ammunition box.
See
https://www.awm.gov.au/collection/C11056
Mike