After binding to NSBrowser indexPaths the browser assumes I'm using NSBrowserCell and calls unimplemented methods on my NSCell subclass

So after binding to NSBrowser selectionIndexPaths: https://developer.apple.com/library/archive/documentation/Cocoa/Reference/CocoaBindingsRef/BindingsText/NSBrowser.html

this causes NSBrowser to do some weird stuff that seems completely unrelated to this particular binding. It starts calling NSBrowserCell methods on my cells but my cell is not a NSBrowserCell. My cell is actually a subclass of NSTextFieldCell. But NSBrowser starts sending setIsLeaf: (which I don't implement).

In any case if I implement the -setLeaf: that solves that unrecognized selector, but now my cells don't draw titles.

Not sure why binding to selectionIndexPaths causes this behavior? The cell stuff seems unrelated to this particular binding. I am of course using the newer but still pretty old item based APIs... do these bindings only support using NSMatrix?

I do set the binding after calling -setCellClass: but makes no difference.

I also just tried overriding -setSelectionIndexPaths: but NSBrowser does not use the setter.