Regular playing time at that age matters, none of the lower level clubs really play in ways that suit us, but learning the grind and physicality will help him develop.
I think the mental aspect will also help. These are truly competitive games. People are playing for their mortagages. He's not going to be given an easy time as he learns. He has to perform week in week out or the other players will be on him. Also lets him see how the other half live. No £100m training centre, with plunge poolsand steam rooms. He'll be lucky to get a hot shower.