How have you not noticed any of them? Most obvious is local storage throws out of space exceptions if Safari is in private mode. I'm not even a web developer.
Honestly, not really. The only one I can think of is your localStorage example.
Regardless, that's not the point. I'm not saying that Safari is perfect, I'm just saying that while it might have some implementation differences and bugs, so do other browsers.
As of iOS 11 and macOS 10.13 Safari does support WebRTC and streaming API. And I don't see them supporting service workers any time soon because that's a stupid fucking idea.
Because private mode is for porn? Who'd try normal apps there?
(only kidding, but it's not the most obvious thing to check and optimize for if you're a web dev. If that's what Safari's problems are, it's pretty solid.)
Regardless, that's not the point. I'm not saying that Safari is perfect, I'm just saying that while it might have some implementation differences and bugs, so do other browsers.