At the very least, they are very interesting to consider. The extreme cases are often useful in helping to think about the paradigm and improving understanding.
Is this the interpretation and behavior we all prefer and expect?
User response indicated the following preferred behavior:
Nodes having no input arcs should fire once at start-up, and never fire again.This behavior is consistent with the START node, which has no inputs and was formerly considered to be a special case. Now, your graphs can, in effect, contain any number of separate start-nodes, and they can be called anything you want.
Status: Implemented as specified.