If it actually works depends on the Widgetset. With QT4 and QT5 it works. I think I remember that on MacOS it does not work with Carbon probably also doesn't work with cocoa.
BUT you can simply use QT5 on macOS.
I never claimes it would work with cocoa (in fact i already doubted this when I made the post). But using qt for mac is (once it is setup) rather easy because you can ship the required dependencies within the AppBundle format.
Its a common problem (or at least it was when i used a mac) that both, carbon and cocoa had some quirks that made some LCL functionality inacessible. Back then neitger gtk nor qt where an alternative (gtk2 required x11 and looked absolutely terrible and qt4 looked like macos 10.4), but if I had to support macos now, i would probably go for qt5, looks native and has a much broader LCL support than cocoa.
But long story short, i already suspected this to not work with cocoa, so either use a different WS, or you simply cant do it (well maybe via raw api acess, but i know way to little about cocoa to answer this question)