First, if you are going to quote something you found on the internet, please share the source with your audience. Without the source it is a guessing game on the reliability and applicability of the information. Your material sounds valid - however all information needs to be understood in context to be fully understood for applicability.
It is important to remember at all times that PMR is a default Dx. This means if it is not other things they test for then they default to PMR if you have certain symptoms and respond well to steroids. There is no definitive test to prove you have PMR. That being true it is impossible to say that PMR is a single medical problem. It could be a compound problem that needs to be peeled apart and treated individually. Even complicating it more - your version of PMR and my version of PMR may have similar characteristics but may not have the same root cause and thus may respond to identical treatments differently. PMR is complex mainly because it is not well understood.