It's neither an exception nor something new. I don't think (m)any of us would be surprised about this sentence. While {-chuq} reduces the valency, making a transitive verb intransitive, {-moH}, being a causative suffix, increases the valency by adding another argument. Intransitive verbs become transitive, and transitive verbs actually remain transitive, but another oblique argument is added (see the famous example with Worf's sash).
Now, any verb with {-chuq} is by definition intransitive, so adding {-moH} naturally makes it transitive again, turning the meaning into something like "S makes O verb each other". I don't recall if I have ever used these two suffixes together, but their use seems quite natural to me and I would've formed the sentence the same way.