Apparently technicians are standing on the damaged area of the fuselage to access other areas for inspection.
If it doesn't say NO STEP and you need to stand there to maintain the aircraft, standing there doesn't seem to be an unreasonable thing to do. Maybe that is why there was that bonded panel on the original piece, to keep it from buckling and punching thru under the weight of shoes.
Of course, if one accepts that it is a step point, it probably affects what the structure should look like. So maybe this isn't a bonding or vibration fatigue failure, but instead failing to design it to be walked on?