You didnt comprehend the meaning of the saying at all did you?
All it means is if you are trying to perform several acts you will never be as good in anyone of those acts as if you were studying and putting all your focus in to just one.
Why do I have to be good or (Master) just one thing, why can't I do both, I mean for crying out loud our job is to get the patient to definitive care right? I don't think I need a degree to do that. I mean unless I am wrong, to me definitive care is a Dr., lab, cath lab, x-rays etc. I don't carry any of those on my rig.