Yes I know. I've got many sets of RF cinch cranks. Usually the non drive side doesn't come with the puller and 8mm bolt, just the one 16mm bolt. That's why spindle kits you buy come with the puller and 8mm bolt, so you can get the spindle off without having to remove and use the one from the drive side.
Non drive side probably doesn't have the puller cap and 8mm bolt like on the drive side. It is probably just the single 16mm bolt that was used to tighten down the spindle. He probably has to remove the 16mm bolt (which is what I'm assuming is the one stuck), then install the 8mm bolt and 16mm puller cap to push the spindle off.
And yes, the crank will take that torque. Think of how much torque you're putting into the crank when hammering up a climb or landing a drop. Way more than you can put on it with a wrench...
50nm is a crazy high torque for a bike part. SRAM/Truvativ crank arm fixing bolts have a rating of 54nm and most cassette lock rings usually have a 40nm rating. For reference, stem bolts are usually between 4 and 6nm. Shimano pinch bolts on their cranks have a rating of 12-14nm each.