I have an M4 Pro, so you have not tested with my specific model.

> I am sure many other people would have noticed if the DFU port was marked incorrectly.

Why? Again, I'm not generalizing to many Mac models. Apple's doc specifies a very limited exception: 14-inch MacBook Pro with M4 or M5 chip.

And among users of the limited exceptions, who would notice except the few who need to DFU or the few who have macOS installed on an external disk? That doesn't sound like so many to me.

> a bug in macOS updater

So vague as to be an unhelpful handwave.

> Just as an example, I have a USB-C flash device that is so flaky that sometimes does not work with a port on one direction and connect/disconnect and flipping the direction works.

This example is not applicable to my case. The external drive otherwise works perfectly. It's not flakey at all. And in fact it boots into macOS Sequoia just fine, and software update on the volume works fine for non-macOS updates, such as Safari. So again, you've given me zero alternative theories.

Moreover, the symptoms that Michael Tsai described in his case of using the DFU port are exactly the same as the symptoms that I experienced.

[EDIT:] I looked around, but unfortunately I don't appear to have the proper cable to perform a DFU test. In fact I usually need to use some damn dongle just to connect to USB-C.