I wasn’t using it in “boiling direct sun”, surely nobody is just parking their baby in the sun and leaving them there.
I used it to shade my baby when, for example, walking between the car park and the library/shop/whatever and it’s brilliant for keeping the UV rays off them.
As I said, I’ve stuck my hand inside many a time and it’s never been hot in there. Obviously if you’re silly enough to park your pram in the sun in 30+ degrees or go on long walks it’s going to get hot in there (or any pram, even with a parasol).