The description here says it "comes with" the TRS jack module, while the Intellijel site says it "connects to" it. I assume the Intellijel site is correct and the expander module is required, but it's not quite clear to me.

That's correct, the trs panel is a separate purchase. This is because depending on your case, you may not need it. The 7u case has the trs jacks built in already. The 4u case does not.

I edited the MG entry to reflect the actual Intellijel description.