Tradesmen do not always know their trade
Be very careful when the builder says he is also a plumber, tiler and painter. Chances are he isn’t. He may have seen a plumber or tiler or painter at work but if he is actually a chippie then he will know how to erect a stud wall but not necessarily how to put tiles on straight.
It is a sobering but important lesson for us all.
Get good at something by all means, but then be honest about it.
Claims of competence beyond what you truly know are too easily found out.