Collaboration processes represent behavior of collaborating cases within multiple process orchestrations that interact via collaboration concepts such as organizations, agents, objects, and services. The heterogeneity of collaboration concepts and types such as message exchange and synchronous collaboration has led to different models targeted by collaboration process discovery (CPD) techniques, but a standard model class is lacking. In this paper, in order to reduce heterogeneity among model classes and to reveal similarities between CPD techniques, we prove that the synchronous collaboration type simulates message exchanges, but not vice versa. This constitutes a step towards a standard CPD model class that achieves comparability between CPD techniques, enables approach and property transfer, and is a condition for a standardized collaboration mining pipeline similar to process mining.