Folks; it’s okay if you don’t like it!
Just make it optionally auto expand/contract for those of us who do.
This is the reason why I use MS Edge over other browser right now.
It’s a deal breaker for people who want to focus on the webpage content and forget for a second that we have 20000 tabs open.
And if we’re talking about “MacOS design guides”, what about the auto hiding Dock? That’s not even minimized it completely disappears.
So suggestion: auto expanding sidebar on hover (opt-in option in settings)