> once properly dried

That “properly” is doing most of the heavy lifting there. The reason i would be weary of running the dishwasher with a toaster inside because i would worry that liquids trapped around thin electric conductors will corrode them. In othet words toasters were not designed to be easy to “properly” dry them out. And that damage might not be appearant right away or after a single wash.

In fact i wouldn’t trust the professor’s claim that the “toaster is perfectly fine” unless the professor conducted a lot of experiments. And even then i would only trust it with the toaster models he tested the claim with.

There even was a HN thread about this anecdote. I remember though that someone there made the counter argument that, yes, the toaster will be fine, but the dishwasher will be full of icky chemicals that you don't want to have on your dishes...

If you eat the apple diagonally down instead of around, the cores are totally edible. Less waste!