OK… I fingered it out. I was able to see the "something cool" splash by enabling "HTTPS-Only" mode in Firefox prefs.
That's probably selected by default. Deselecting it eliminates the redirect.
Safari (naturally) does not have a user-selectable HTTP/HTTPS mode selector.
I suspect if you look in Chrome prefs, you'll find it on - if it's selectable at all.
Amusingly, in Ffox, manually typing -HTTPS://macos9lives puts up a warning page telling you that horrible things will happen should you continue down the path to Hell you have selected. You can however, elect to go there anyway but that drops you at the "something cool" page and that's as far as you can get.