We may without restriction assume that every hom-$\infty$-groupoid is in fact a set on the nose. Then since this is (-1)-truncated it is either empty or the singleton. So there is at most one morphism from any object to any other.

A $(0,1)$-category which is also a groupoid (that is, every morphism is an isomorphism) is a $(0,0)$-category (which may think of as either a $0$-category or as a $0$-groupoid), which is the same as a set (up to equivalence) or a setoid (up to isomorphism).