If shard catalog metadata is invalidated or updated while a recoverer is already running, the recoverer will be the one in charge of processing the event using the OplogEntry timestamp as its reference. On primary nodes, however, that timestamp is 0 because the opTime field of the OplogEntry is cleared by repl::logOp(). Consequently, if recovery is already in progress, invalidating or updating shard catalog metadata has no effect on primaries.