Are Safari tabs documented (maybe unofficially)?

We all know that Safari doesn’t have Applescript support for tabs. :frowning:
However, I found some Applescripts manipulating Safari tabs.
Usually they contain code like this:

--Count the number of tabs
set tabCount to count radio buttons of window 1

repeat with i from 1 to tabCount
-- activate each tab
click radio button i of window 1

And it works!

Apparently radiobuttons are used!?! Radio buttons??? Where?
Where is this black magic documented?
I want to learn more!

Scripts like that are taking advantage of Apple’s UI scripting mechanism:

I agree it’s kind of funny that they are identified as radio buttons, but apparently regular tabs in a Cocoa tab view are as well.