The point of the harness was to hold them upright, in case they passed out while being winched up. If the cage stuck the idea was for the passenger to detach the lower half, and be lowered.
................

Incidentally the chant that was roared out when the miners came up was

"CHI CHI CHI LE LE LE, LOS MINEROS DE CHILE!" - a reworking of what Chile's football supporters use at international football matches - "CHI CHI CHI LE LE LE, VIVA CHILE!" (For example here.