With MLPPP, the counter on LNS side is only available for the bundle, not for each link, so the SR OS’s behavior is:
For each new link session system sends a tunnel-link-start.
For each link session that is deleted system sends a tunnel-link-stop.
For all link sessions except the last one system reports 0 for all counters.
For the last link session, system reports the actual counters for the bundle.