Damn. You're right. Bad assumption on my part.
The summoning ability for those commanders must have been in earlier CBM, I assuming all the while that they were vanilla, rather than a change introduced in CBM and then later removed from CBM.
Well then. Never mind my half-baked theory on
that. Go on about your business, nothing to see here.
EDIT: (I saw Sombre's post after I wrote this.)