I think that's right, search.remote.*.transport.ping_schedule isn't a setting, because the per-remote-cluster ping schedule was introduced in #34753 (i.e. 6.6.0), which was after the search.remote.* settings were deprecated in #33413 (i.e. 6.5.0). I don't think it should be possible to set search.remote.ams01.transport.ping_schedule. Are you sure that search.remote.ams01.transport.ping_schedule is set?