Apparently pre-rinsing confuses the dishwasher or something. Not doing it leaves me with residue all over the other dishes though 🤷
It's an American thing. Our dishwashers get hot water from the line, there is a heating element, but it is not very powerful due to our lower output electrical sockets.
I've heard other countries have washers that are powerful enough to heat their own water, which is why they are attached to the cold water supply.