Variable outputs can be described by rules
Even granting that a given state of a connectionist network could lead to a variety of further states, a set of rules could still be formulated to describe its behaviour.
This is because rule forms have:
"implicit conventions of simplification when a single input representation might lead to distinct output representations".
So, the syntactic argument holds.
Kenneth Aizawa, 1994, p.484.
Note: The debate between Aizawa and Horgan & Tienson about rules is carried out with much more precision than could be captured here. In the technical discussion, issues of quasi-exceptionless rules, probabalistic laws, and ceteris paribus rules are raised.