My expectation is described in the comment you replied to and side comments
Microwave's ding is also bad UI, especially when it's repetitive as it's just useless noise. But even the first ding - what value does it have if you already have exactly the same notification category - audio cue - built right there in the process: the machine noise disappears when it stops working.
Brains work just fine and your typical kitchen/apartment range is small enough, but in general - the trade-off between comfort and reliability is not something you can resolve for others