I don't know exactly where the line is between street art and graffiti.
The one you are referring to is in zone where the painting on the wall is allowed. It won't get overpainted anytime soon by a "rival artist".
So, I agree it can easily be classified as a "mural".
A matter of interpretation indeed.
I took the street art thread more meant for, lets say, official artworks and this one for spray painted artwork.
There's also graffiti that's more akin to vandalism. In my mind, that is what it is then, vandalism. I wouldn't encourage that by posting images of it.
But that in itself would be open to interpretation as well