The manual could have said not to leave the baby or the dog in the car when solar vent is the only form of cooling. Likewise, microwave manuals could tell you not to put the cat in the oven. Problem is that the more specific the instruction, the greater the chance of an idiot doing something equally insane. Alternatively, it could be referring to the little known fact that radiation from the solar roof causes permanent male impotence after five minutes exposure.