By the way, before you come back and say “I like how it works in smart lighting, why doesn’t work that way in routines? I have things I want to activate when a Mode changes that are not available in Smartlighting.” There’s a trick to it. Again, this isn’t documented anywhere, you just have to learn about it in the forums.
Smartlighting can turn on a switch. Any kind of switch, not just a light. And it can even be a virtual switch.
And You can trigger a routine when a switch is turned on.
So…
One) create a virtual switch
Two) create a smart lighting automation that turns that light on when the Mode changes, as in the screenshots above.
Three) create a routine that is triggered automatically when that switch comes on. ( also have that same routine turn the trigger switch off again, so it will be ready for the next time.)
Bingo! Now you have a routine that starts when the mode changes.
As for other questions:
I don’t know why it works differently in smartlighting and in routines. It just does.
I don’t know why they didn’t make the “when mode changes” trigger available in routines, they just didn’t.
Welcome to SmartThings!