I've been "visualizing" (another word for guessing) what something like this might sound like for a flugelhorn bell...
I think it might enhance the lower harmonics and maybe even give the player more feedback?
The drawing has some errors...the "hole" in the side view should be black, and the end view is shown without the end plate. The end plate would have a single hole in the center.
A fine gentleman shared with me that having holes in the ordinary bell of a trumpet improves what the player hears, and thereby lessens the sense of stuffiness.
I can't see this working for a trumpet but had a hunch it might make for an interesting addition to a flugelhorn.
Full disclosure: the shape was born from an old expansion chamber I used on my racing gocart forty years ago. I remember liking its baritone hum.