The problem is if the temp is 102 on top of the substrate, depending how deep the substrate is, it could be a lot hotter directly on the glass. Also high temps can cause neurological issues with snakes. That's why you shouldn't go above 95. I mean sure the snake can move but if for some reason he doesn't feel secure in the cool hide as much as the warm hide, he will sacrifice correct temps for security. The same goes for cool side, he can get too cold sacrificing the need for security over the need for heat. That's why you should try and use the same hides on both sides. And snakes burrow too, so he can easily get to the glass which could be a lot hotter. Generally you don't want anything lower than 75 or higher than 95.