You've just made four hard boiled eggs in a small pot
You dumped out the water ten minutes ago. The pot is cooled off, and empty. It only had whole eggs in it, still in the shells. Now tell me, do you wash that pot? Get out the sponge and the soap and scrub it like usual? Or do you give it a quick rinse and slam it in the drying rack? No judgement here, only curiosity.
I boil with salt and a bit of vinegar in the pot. When I'm done, there is a noticeable white coating on the pot, presumably calcium from the egg shells.