"If a verb with the suffix -ся is transitive, however, its object will not take the accusative case but will require one of the other, oblique cases."

Transitive means that the direct object can be made a subject of a passive sentence, which is not possible here. The direct object is in accusative case. Such verbs take objects, but they are no direct objects, the verb cannot be transferred (is not transitive). Therefore these verbs aren't transitive.