Entubado (entubar) is old-school bunching: each filler leaf is rolled into its own tube, then the tubes are gathered and wrapped in binder. The idea is orderly airflow — a draw that is neither a straw nor a plugged stick.
It takes time. Many factories use faster folds. Houses that still teach entubado treat it as a craft method, not as a magic flavor machine. A sloppy tube bunch smokes worse than a careful accordion.
It is construction. The tobacco still has to be ready. See how cigars are made for where bunching sits in the long process.