All material movements are posten when manufactuting order in status done.  In an eallier version I remember it was possible to post goods movements without that.  If you partly confirm an order you get the option to create a backorder.  But you cannot post consumption of only components.

Then also there is no check that you over consume a lot number and en up with negative stock figures.  So yes, you can always choose to enter a lot number that has already been totally consumed.  But if you if stick to what has been allocated with availability check, it should be correct.