Likewise, I've only ever seen it once (in person, but I've seen plenty of photos of the tail lifting, without shearing).
The one I saw had apparently been bending for a while, when it suddenly just ripped - I wouldn't say it took out a bunch of wood, but it did some damage.
I'd guess that the person responsible for the mod in the O.P. probably had more confidence in putting in a new block, and attaching the new bridge to that, than to carve something that fits into the existing cavity (which has clearly been extended), and then attach the new bridge to something with pre-existing drillings, and new wood joins, in all the wrong places... But all we can do is speculate.
The one I saw was a black tailpiece at the rickresource forum probably close to twenty years ago, there was also an 'exploding' R tailpiece which I still think is kind of funny.
