Yes this is so true and i believe all most all masters do it a lot here. And even without teaching your apprentice all you know there are other things the apprentice can know without knowing one thing in this life is we can't know all so definitely the master can teach his/her apprentice what they know and the apprentice can also get other information of same thing from other people but different method.In Nigeria, most artisans don't like teaching their aoorenticws everything because they feel the apprentice might grow more than them.