External shear loads in the Profis concrete-to-concrete module

In Profis's concrete-to-concrete module, why is it not permitted to apply an external shear load when using the anchorage provisions to design the connection? When I try to do that I get the warning "Anchoring-to-concrete to design for external shear loads is not an option when shear load is added. Please switch your design method to one of the other options."

Edited 3/14: I should also acknowledge that the user information in Profis is very clear that this is a constraint - "A user-defined shear load cannot be used with anchoring to concrete to design for external loads" - I am looking to understand what the technical basis is for this constraint.