Question: Why are eclipses of the James Webb by the Earth or Moon not permitted during the mission?

In https://ntrs.nasa.gov/api/citations/20150017756/downloads/20150017756.pdf. it is stated

Shadows, or eclipses of the spacecraft by either the Earth or the Moon, are not permitted at all during the mission… these constraints conspire to limit the maneuverability of the spacecraft and couple the orbital dynamics to the rhythms of the Earth, Moon, and Sun.

How come? The cold “science” side of the spacecraft is already eclipsed by the sunshield. Communications interruption should not be an issue since communications are intermittent anyway. I assume there is enough battery capacity that solar panel eclipse is a non-issue. Likewise with light sail pressure eclipse.