Is this input:

+Y (mu = 0.1)

a shortcut to represent a sliding shoe support with friction, where the actual restraints present are:

+Y
X (mu = 0.1)
Z (mu = 0.1)

I've come across the first version in a colleague's work, but can't imagine it's equivalent to the second. (If it was, then there'd be no way to input the vertical restraint with friction that the first input actually suggests.)

Is this a shortcut that I don't know, or a mistake?