In some sites, especially FoxNews, Reader Mode will claim it's in wide mode while it's really in normal mode.
Navigate to FoxNews.com. Select a story, enter reader mode, enter wide mode of reader mode.
Exit.
Navigate a new tab (or Cmd-Click a story open into a new tab) in FoxNews. Reader mode usually correctly comes up; if it doesn't, open it.
Observe that it is middle-width.
Open Reader Settings.
See it is at widest width.
Set to middle and back to wide, see it gets wider.
You can repeat this endlessly.
Demonstrated in the video below.
Expect Wide Mode preserved for the entire domain - which it thinks it is, and for wide mode to be wide.
Failing that, expect Reader knows it is not in wide mode.
Version 0.99.128.2.1-rc (WebKit 619.1.11.111.2)
Sonoma (14)