Silica gel can be recharged in an oven, but not silica clay (kitty litter). Silica clay is a one way process (absorption only), but silica gel has buffering capability. So if he starts with silica clay that is already full of moisture, why use it? Like I said, you need a way to measure the moisture content to know if it will absorb more moisture. If it were me, I would just buy the silica gel which lasts forever.
Not arguing with your preference for silica, but I find it impossible to believe that clay will not release water vapor when baked. I’ve seen an awful lot of clay suck up water when it rains, and then turn to dust in the sun.
Is that true? Scoopable litter cooked in an oven will not release its moisture?