It would be unfair if it took no time at all.
why do premoves take time
why do premove take our time 0.1 second we premove that move so it should take no time
Because the site decided a long time ago that premoves should take time.
https://www.chess.com/blog/DanielRensch/bullet-chess-philosophy
why do premove take our time 0.1 second we premove that move so it should take no time