The Mag should have no problem dubbing a true 16:9 program recorded on a digital channel to its own HDD in "16:9 Wide" (setting in Video > TV Aspect) to a DVD with same setting, and TV set to display Wide, or stretched, or whatever. Only real unknown is if played on a different player/recorder, but mine play nice on Panasonic, Samsung, and other devices here.
Did you use HIGH (high-speed dub, HSD) or real-time dub? Might want to try a recording with proper settings in SP, dubbed to DVD with HSD, and see if any diff under same conditions.
Assuming you have your Magnavox set to 16:9 wide you should be getting anamorphic recordings. Now the Magnavox like almost all standalone DVDRs don't set the WS(wide screen) bit but the way around that is to set your DVD player to WIDE or FULL for 4:3 discs, if your DVD player lacks such a setting then most all 16:9 HDTVs have a FULL or STRETCH setting that will decompress the 4:3 anamorphic recording and display it in it's proper 16:9 aspect.
The WS bit is what tells your DVD player to stretch a 4:3 anamorphic frame to true aspect 16:9, all WS DVDs including commercial are recorded in this format, 4:3 is the format for DVD but by utilizing anamorphic recording one can store a 16:9 frame in a 4:3 container.
The downside to that setting is even when you play a non anamorphic DVD it will still stretch the 4:3 frame to 16:9 resulting in stretched or fat people, if this really bothers you, you can change the setting back, but with me the vast majority of the things I play are 16:9 so I generally just live with a few stretched 4:3 programs, besides as you said it gets rid of the wide black bars on the side.
Lastly even with the setting set to stretch 4:3 material to 16:9 it will not double stretch DVDs that are anamorphic and actually have the bit set(like commercial DVDs) so no worries there, commercial WS DVDs will still look correct.