Widescreen burned DVD plays 4x3 not 16x9
 

I have a Panasonic Blu-ray player. It always plays my homemade DVDs in 4x3 format instead of 16x9. The same discs on plays 16x9 on my Magnavox DVD recorder.

Is there a setting I am missing in playback?

Homemade DVDs are commonly flagged wrong by the DVD recorder. DVD recorders are really pre-16x9 invention, and adding widescreen recording is a hack. The DVD recorder understand this, but your dedicated DVD/Blu-ray player will often not. Furthermore, be wary of the widescreen settings on both the recorder (in both recording and playback modes, if applicable) and the DVD/Blu-ray player.

It varies not just brand to brand, but model to model within brands. So it's hard to give anything but general advice.

When I rip DVDs recorded on Philips/Magnavox DVD recorders, I have to run the M2V video files through Restream to flag it properly. Only then will the assets be acknowledged as 16x9 by editing and authoring software.

I should have been more specific in my original post.

These homemade DVDs are of 4x3 TV programs that I have converted from VHS tapes.

My question is why doesn't my Panasonic Blu-ray player automatically "expand it" so that it fills my entire TV screen at 16x9?

It's not supposed to.
If the video is 4x3, it's supposed to play with "black bars" (pillar boxes) on the sides to maintain aspect ratio.
It's not supposed to stretch the video oddly to fill the 16x9 screen.

This is both normal and desired behavior.

So, you are saying that the Magnavox's ability to do so is an anomaly?

Not so much an anomaly as much as it's not properly compliant to DVD-Video playback.