Ad-hoc sub-process audit rules

[marco64io]

If I right understood BPMN specifications, in an ad-hoc sub-process I can put more tasks without control flow among them and I cannot put start and end events. Well, if in Modelio 4.1.0 I create, in a BPMN process diagram, an ad-hoc sub-process and in the diagram of this sub-process I put two tasks without control flow, I get three errors in model audit: a rule R3080 violation for each task and a rule R3250 violation for the sub-process, that seems in contradiction with BPMN specifications. This seems a bug if I'm not doing something wrong