this sounds like an old wives tale being passed around some ignorant installers.
1. Why would the sun roof be different from the side windows, or the windshield.
2. Ceramic tint blocks heat, (it does not allow it to pass through the film) it should not absorb heat and hold it against the glass.
3. Older films that were dark, blocked visible light but transferred heat into the glass… this is obviously contrary to why you are paying more for ceramic tint.
Do a Google search, there are a couple hundred articles on this.