An army can have good overall morale, and still have frontline soldiers complaining on the phone, especially conscripts.
That’s my point. Selective release of intercepted calls of soldiers complaining, or otherwise expressing negative feelings isn’t unique to armies with poor morale.
The Ukrainians are still humans. They aren’t zealots, or robots. Humans have complex feelings, and they communicate those feelings, sometimes in ways that can be intercepted by enemy surveillance.