Hey there,
Same frustration here, would love to see the manufactures response to this, since this is not mentioned anywhere on there website. Also on other tutorials, this procedure is not mentioned. I was wondering if this is an issue related to Arduino and the way it uses the upload tool. That is why I’ve also tested it with PlatformIO, but also no luck there.
I am wondering If there has been a change in the bootloader that caused this. Again, I would like to see some response of Seeedstudio to shine light on this topic. The waiting game I suppose…