Thats of course true of all Enfields from the Long Lee onwards, but I think by then the use of the cut-off had moved away from single-loading and onto a safety function. In the (very short) era of single loading, the Lee Metford had both a fairly soft extractor spring and the rounds itself had a rounder case rim. We'll probably never know, but single-loading was probably abandoned at the same time they changed the extractor and cartridge case - possibly they wanted to achieve a more positive extraction, and the realised that a harder extraction spring would necessitate magazine feeding of the round?
I think its quite fascinating how the upgrade from Lee Metford to Lee Enfield reflects the combat experience with the (then) revolutionary magazine rifle - its clear that after Sudan and NW Frontier conflicts, the Army suddenly comprehended the rapid fire potential of the rifle, and the effect that would have on tactics.