Indeed, my searching seems to indicate the same.

I also found this program, which seems to work well, though I have only tested it a bit:

http://sunsky3s.s41.xrea.com/dmgconverter/index.html

It seems to create valid raw images, given a variety of formats, fairly easily. I also ran across an old hint that additional formats can be enabled for Disk Utility, using the following:

In my (limited) testing, on 10.8.5, it does enable the formats, but trying to create a Disk Copy 4.2 image from an existing UDIF image caused an error. I'll post more, as I do more testing.