I admit it’s a touch more complicated than just powering it up, but I also think it’s a relatively creative way to separate the RPi power requirements from the HAT requirements. The need for a clean power supply to power the HAT is a factor to consider though.
I can see where one would think there’s a specific power up sequence, but that’s not the case. You can have both plugged in at the same time. It probably would be more accurate to say to not plug in the clean supply after you power on the dirty RPi side. But I most certainly do not unplug and replug when I perform a shutdown or reboot. Both power lines stay in Signature.
The only pain in the ass issue, for me, is the 2.5 to Type C adapter since most power supplies seem to be 2.1. But I expect we’ll see more options for Type C as the industry begins to pick it up.
Edited to remove the part about using the Signature with only dirty power. I thought I had this tested this past weekend, but tried to repeat it and it didn’t work. Sorry for any confusion.