Regarding the OP’s original question–I have never noticed pelleted bedding clumping/packing in horses’ feet, at least not to the degree that it doesn’t all fall right out when I pick the hoof up. No digging or excavating necessary.
Not sure if it’s the particular pellets or the way they are being used by our B/O. Most of the stalls are just a very fine dust.
With any moisture at all they seem to be packing in every crevice of ours and others hooves. It doesn’t just fall out. It gets packed in solid and has to be picked out. We have some concern what is being packed is urine soaked pellet dust.
Our horses are in stall about 8+ hrs during the day and are out at night.