yes, that is true. Disk Utility erases CDRWs (otherwise I would have run out of media for my frustrating tests! ;-)
Here's an interesting update -- inferring from JackShedd's post that some of the X apps might be able to write single-track CDRWs, I tried and was successful in burning a disk image to CDRW via Disk Copy in my Firewire CDRW drive. (I haven't yet tried single track with the Finder or Toast P2).
The strange thing is, though, that the CDRW onto which I successfully burned the .dmg reads fine in my built-in (expansion bay) CD drive, but will not read in OSX in the CDRW drive in which I originally burned it! What is up with that?
I also tried to read other CDRW media (burned elsewhere at another time) in the Firewire -- a CDRW onto which I had burned CD audio tracks showed up in the Finder, but a CDRW onto which I had burned mp3s did not show up. Both of these disks read in OS9. So it is not just that the CDRWs I just burned are not showing up, but no CDRW is showing up unless it is CD audio.
is it possible that the X support for CDRW is somehow so limited that it won't read CDRW media across Firewire, other than audio tracks???
My setup:
Powerbook 333mhz G3 Lombard ("bronze")
320RAM
4.5HD w/ 3 partitions (3.1GB, 650M, 650M)
Keyspan Firewire Cardbus card
EZQuest BOA CDRW 16x10x40