I managed to get this feature to not work for me for some reason. Tried downgrading from 3.674,1805 to 3.626,1778 but it didn't help.
The goal is to disable BetterTouchTool altogether on Safari when it hits YouTube so I can have default media keys etc and enable it back once YouTube is closed.
So what I did is I clicked on "Create conditional activation group", set "Window Name" "ends with" to "YouTube" and "Bundle Identifier" "is" to "com.apple.Safari" and also enabled "Disable BetterTouchTool completely".
I suspect this stopped working after I added a Group to Safari, grouping all my most important Bookmarks. In this Group I have actions that use "Open URL" and "Close currently open Touch Bar group".
In your screenshot it looks good - if it's green then your condition is matching the current window.
And this does not seem to work? Does BTT disable if you remove the window title/name condition and just leave the Safari condition?
It doesn't hide BetterTouchTool Touch Bar to show me the default macOS Touch Bar with media keys that are shown when YouTube playback starts, including the PiP button.