As you know, you "stuff" during the charging process. Electrons in the battery. The less space there is = the closer you are to 100% SoC (state of charge), the more they rub against each other = waste heat in the battery. It does not particularly like to operate the battery outside of its temperature window due to longer-term durability. You can only cool to a limited extent. And cooling means energy expenditure in order to transport away energy losses. That is why even Audi with the e-tron has a massive drop in charging power from around 80% SoC to the max. Charging power is kept very constant. However, it should still be cooled to maintain the temperature window.
If you discharge the battery, the state of charge will decrease over time or you will not stuff electrons into it, which will then become narrower, but will have more and more space (even if there is natural heat again if you discharge the battery strongly) , but at least there is more space so that they no longer rub against each other so much).
