I ordered a new Bosch dishwasher from Home Depot. The

Hello, this is Brandon, your appliance expert. Newer Bosch dishwashers are designed to use their own junction box, which officially can connect to a hard wired electrical cable instead of a power cord going to an outlet. Depending on the location of the existing electrical wiring though, it may not reach where it needs to for the manufacturer's requirements.

There could also be limits created by local building codes, or by company policy of the installers - I have not heard of this overheating issue, but it is possible that particular company had dealt with several warranty or damage claims resulting from wiring issues and so made a company policy to not install with that method.

As for specific requirements of the manufacturer, those can be found in these installation instructions:

https://media3.bosch-home.com/Documents/9001244448_A.pdf

The electrical requirements are on pages 11 - 13, if the hard wiring can't be routed so that the junction box is in an accessible cabinet adjacent to the dishwasher (page 13) that would be the main potential issue I could see, a lot of hard wired dishwashers have the wires coming from directly below or to the rear.

Otherwise, I would expect the wiring would be the correct gauge, as long as it is 3 wire and in the correct location it should be possible to use per the manufacturer. I can't speak to any specific company policies or local building codes but this is not something enforced or advised by the manufacturer.