It's not necessarily the firmware for all the iApps and Finder, rather with device profiles.
It appears only dual-layer buring in iDVD that is sensitive to the firmware version, probably using a firmware check -- but I can't say for sure on that. Apple OEM optical drives usually have different firmware from the ones that you buy, and usually this doesn't make a difference. One verified problem with different firmware came in the early days of OS X, where drives with PC firmware would cause kernel panics on wake if you left the disc in the drive of Pioneer Superdrive. There was a workaround for this, and I believe, but haven't checked that the was later in later versions of OS X.
With Finder and iTunes, the issue isn't the firmware of the drives but rather with device profiles (files or files). Going back to iTunes and disc burning on OS 9.x Apple was and still writes and updates these device profiles as new drives hit the market -- so the various apps know what drive is installed and being used. This is why for instance the Pioneer 109 didn't have support early on with Tiger, but the 10.4.3 update brought native support (without the need for Patchburn).
So if the drive you're installing, e.g. Pioneer 110D, is too new, and Apple hasn't yet written the profile for it. Part of what Patchburn is to supply the requisite profiles for these drives that are too new or drives from manufacturers, Apple may have never officially supported. A lot people thought the 10.4.4 update would bring full native support for the 110D, but alas it's still not there -- I checked when I installed mine. I've installed a lot of Pioneers over the years, great drives which Apple still uses. (Just installed a 110D in my DA, and a K05 in my PB and Cube.) Usually get full compatibility with these -- I say usually since there is the issue of the iDVD5 dual-layer burning. We'll have to see if iDVD6 removes the alleged firmware check.
If you're still stuck in 9.x, you can find patched device profiles at xlr8yourmac. I used one with a Pioneer 106.
DA-Giga 2x1.33; Cube-Giga 1.3; PB 15" 1.33-Hitachi 100GB 7K100, Pioneer DVR-K05 Mac OS X (10.4) Cheetah 15.3K, ATTO UL3D, Radeon 9600 Pro