That isn't true; scrolling (and resizing) was a performance sinkhole for all kinds of apps that used the native table views (NSTableView and NSOutlineView), for

That isn't true; scrolling (and resizing) was a performance sinkhole for all kinds of apps that used the native table views (NSTableView and NSOutlineView), for many generations of Mac OS X. They eventually added enough optimizations and performance cutouts to make it pretty easy to not fall in the hole with your app, so it hasn't been a problem with AppKit (or its younger 85% clone, UIKit) for a long while. But I'm not surprised to hear Apple's much newer and not-very-related UI toolkit still has lots of those problems. That's one of the problems when not many developers actually use a technology — it's not just a popularity contest, having lots of users who complain is how you find a lot of the bugs and performance issues in your UI toolkits and app frameworks. So lack of popularity often does mean there are probably a lot of those.