Can you think of any other 2.35:1 DVD releases from 2006 that were non-anamorphic?
No, but that doesn’t have anything to do with what I said.
It doesn’t matter really since most modern players can crop and zoom a non-anamorphic disc.
It still matters if you have a display which can take advantage of anamorphic DVDs. Cropping and zooming is just a kludge. It doesn’t give you the extra resolution that anamorphic DVDs have. Of course, all DVDs have the same resolution (720 x 480 for NTSC), but anamorphic DVDs use more of the available resolution for picture content, whereas a letterboxed non-anamorphic DVD wastes more of the available resolution on black bars (letterboxing).
With a standard-resolution CRT TV it doesn’t matter, because the effective increase in resolution isn’t noticeable, and there are no display format issues either, because anamorphic and non-anamorphic DVDs display exactly the same on a 4:3 TV, assuming your DVD player is doing its job properly. Note that standard-resolution, 4:3 CRT TVs were still being sold new in mainstream stores until at least 2007.