Mr-TM i think you mean shackle guard. Looks like a machine translation artifact.
Anyway, a shackle guard makes it harder to insert shims, bolt cutters or wrenches to bust the lock, but that just means it takes more time to remove it because you need to gradually cut it off with a grinding disc or a drill bit or something along those lines, instead of just ripping it off the belt in a single motion that takes half a minute once you have the tools.