This is not a bug: from the 21w08a notes:
"The cobbled variant is the same but without the top texture"
update: make a twelve block pillar of sand ontop of a piston and hook it up to a TWO CLOCK (repeater on 2 ticks and another on 2 ticks) then sand will break
you can not use a 1 clock, you need to place the torches yourself, I don't know why
This is not a bug: from the 21w08a notes:
"The cobbled variant is the same but without the top texture"