Due to someone reclining or not. The base of the seat where my knees are at stays in the same place regardless. I’m not great with geometry but if the top of the backrest only moves 2 inches and the bottom stays fixed, that isn’t a huge angle and maybe you lose 1/2” or so of space for your drink or laptop. But amazingly you gain that much space back when you recline your seat. It must be magic?