After being told that the changes to a bug report aren't valid*, I decided to look into how hard it is to simply take broken functions off the menu, from the user perspective.
To remove the plt conversion as an option, I found that simply moving the Contents/Resources/extensions/plt* files to a subdirectory took them off the menu in the save dialog. For whatever reason, the HPGL and SK1 conversions work and I assume they draw on the same libraries.
That seems to be the simplest solution to the frustration of seeing features you can't use. No changes to executables or removal of dependencies, just making a broken option invisible. If it gets fixed at a later date, an update script or a new point release could be made available.
I'm sure this seems like a trivial issue for most, but if broken dependencies/features illuminate why the OS X releases are out of sync with Windows and linux, it seems relevant. I don't see why an external function should add to any delay in getting a release out the door, if references to it can be easily removed and restored.
I thank the developer(s) who persevered and built these Inkscape RCs, not only as updates but making it into a full OS X app, getting away from X-Windows.
* https://bugs.launchpad.net/inkscape/+bug/1187197 -- Paul Beard
Are you trying to win an argument or solve a problem?