What is the main physical feature driving the argument that the Boykin Spaniel's covering is technically 'hair'?

Answer

Its minimal shedding profile

The minimal shedding profile is the main feature driving the 'hair versus fur' argument, often attributed to the coat favoring a longer anagen (growth) phase.

What is the main physical feature driving the argument that the Boykin Spaniel's covering is technically 'hair'?
DogbreedhairFurBoykin Spaniel