In reply to Firestarter:
> The loop at the fronts help tuck away the excess webbing
These loops are also present on my DMM Maverick harness which does not have adjustable leg loops, and thus doesn't have any excess webbing to tuck away.
I don't believe the loops in question are actually
intended to serve any functional purpose when the harness is in use. I reckon they're there for constructional reasons: it allows the edge binding on the padded part of the leg loop to be made from a single length of tape which loops at each end and is sewn together at the point where the rear supporting tape attaches. It saves having to put a neat, non-fraying finish on four ends of binding tape.
So they're not designed to be take any significant load, and it seems likely that using them for such a purpose would be (a) unsafe, and (b) likely to damage the edge finish of the padded part of the leg loop. There's nothing to stop you making use of them for other purposes which wouldn't be expected to impose a significant load, such as tucking away the loose end of the leg loop adjustment webbing on a harness which has that feature.