Very wise reflections, thank you.
Your experience indicates how subjective & personal the notion of understanding someone's accent can be. I, as an example, understand Murray better than I do understand my friend from Edinburgh, who lives in Australia for some 25 years but who proudly maintains his accent and does not want to "lose it". I also know a man from Glasgow who is now 80 and has been living in my town for 40y+ but speaks so different to anything I've heard before that a conversation with him is a real challenge for me. He has no trouble understanding me and everybody around but he refuses to "blend in" with his speech.
I'm becoming familiar with many dialects and accents and to be honest I don't care anymore how they are called, especially if they are processed by my brain with no trouble. So accordingly, I'd call Murray's accent not Scottish bit simply "Sir Andy Murray speech". A unique melody of voice owned by himself only (his brother & mother speak differently).