I’ve tried this as well, and have reported it as an issue to RC support.

In our case, the Message Only extension doesn’t even appear in the Analytics - the only way we can see calls to that extension is via the Call Log.

I’m sure I’ll get back the “We’re currently looking into it...” BUT, if I hear anything back that’s constructive, I’ll post.

Call you Account Rep and poke them about it as well - and/or open a ticket that it’s missing from the Analytics.  More voices might get noticed.