Is this really a new thing? It feels like they've just crammed a sliver of the same bog-standard parsing we've been doing for decades back into the CFG. I gues

Is this really a new thing? It feels like they've just crammed a sliver of the same bog-standard parsing we've been doing for decades back into the CFG. I guess that's good for preventing off-by-one-based parsing errors, but surely there's prior art from long ago.