Hey Steve,
the data plane behavior on LDP is swap oriented, while the data plane on SR is pop oriented. depending on the hardware capabilities in use this may have (subtle) traffic engineering or diagnostic implications at a minimum. folks will likely have to build tooling to address this.
I think you're thinking of SR-TE, SR in normal LDP-like use case would be single egress label with swap on LSRs. Ingress PE would figure out label by using egress PE index as an offset to next-hop P's label range. Nexthop P would swap the label determining out label using same mechanism. I practice operators would configure same label range in every box, so swap would be from same label to same label. But that is purely due to operator configuration, and it's still swap. -- ++ytti