The theory behind the Emergency disk is sound. What do you mean?
It is in theory, but in execution it fails.
If you have no working Amiga, the CD is just short of useless. You need 3.1 floppies that haven't gone bad plus access to the internet on a PC to get a CD Driver for 3.1
If you do have another working Amiga, especially if you need an RTG driver, the emergency floppy maker isn't selective enough with what it copies to the floppy and it quickly runs out of disk space even with a high-density drive.
If you don't install RTG software or know ahead of time to set it to an interlaced mode using OS3.1, the default screenmode isn't tall enough for the screenmode prefs app to allow you to change resolutions. The Accept/Try buttons are far off the screen so you can't accept the change.
The install was so painful that I can't imagine they ever did a real-world install during testing. If they tested at all.
At least on the Toaster/Flyer install we included a floppy with a CD filesystem to bootstrap the install from CD.
Not having a minimal boot floppy included with the OS3.9 CD was a terrible oversight.
Also, every Amiga owner should take advantage of the way AmigaOS works, and simply copy their System partition to another hard drive or CD/DVD for backup.
That's great assuming you have a working system at some point, but AmigaOS won't get you there on its own without a stack of shareware floppies on hand.