"Add to homescreen" broken?

[the_bertrum]

I had cause to create a new "homescreen app" to a moode instance on my Pixel 6 and found that the newly created one no longer opened a fresh fullscreen chrome window with no address bars as I would expect, but instead launched the interface in a fresh tab of a standard chrome instance.  Previously created homescreen app icons still work as expected, it's just newly created ones that are mis behaving.

I've tried Chrome and Vivaldi which both are broken, and Brave, which behaves like Chrome used to.  I wonder if it's something to do with the underlying chromium version.  Anyone else find this is happening?