I have not seen this before, but despite its odd look, it leaves more metal in the tumbler shaft, i.e., a more solid tumbler shaft, and I've seen a good number on American rifles where the shaft has snapped off at the lock face, from a hole through its center. It also looks like it would retard the hammer after years of use from starting to get a little loose on the shaft. If the tumbler's screw head is big enough to hide the entire "ugly" off-center hole/shaft, it may be a decent idea.
Shelby Gallien