Like I said it all depends on if the distro supports the southbridge (Nvidia nForce3 250 MCP) at DVD boot up. The "boot up OS X" and the
"installation OS X" are not the same.
The DVD boot up extension.mkext you tried held no Nvidia nForce3 250 MCP support. Tiger must have.

The boot process rougly is: EFI boot starts, the boot.plist gets read, the kernel gets loaded and then the kexts are being loaded.
The soutbridge kext is loaded very early to provide access to the harddrives. Some of the last kexts are video and ethernet.

Mainly the soutbridge (and maybe keyboard and mouse ps/2) are needed to install OS X. To get there the kernel, the southbrige (and video) have to be supported by the distro you choose. If not so, you have to provide the kernel and southbrige yourself via the Boot 132 customized disk and do a retail install.

As the "boot up OS X" starts it searches for (or loads) a (or the) appropriate southbrige kext. If succeded it continues to load from the setup DVD (it recognised the DVD drive), if not succeded, it presents you with a "still waiting for root device error".

The trick is now finding the "right" distro (unlikely) or finding the Nvidia nForce3 250 MCP kext (most likely) and putting it
and some other kexts on a Boot 132 CD.

It is some efford, but if you got a perfect working Boot 132 disk and have installed retail, you are the king of the hill. No distractions through
distros, 100% OS X as near to the real thing as possible. No reliance on some upcomming distro update. If you do it right you even can
update trough Apple software update.