but it works locally (dropping on local mempool) and other nodes may (re)broadcast it again (read ranochigo post)
thus the unconfirmed transaction goes back into (local) mempool again as new unconf.tx
it would create never ending loop which only breakable by RBF or successful double spend transaction
but by setting certain synchronized time based on block number similar to lock_time,
the unconf.tx will be dropped completely by all nodes and never be re-broadcasted again past specified block number
or I misunderstood the way that protocol works?