When I compile le with latest MacOS SDK, the scrolling is broken. Looks like line insert/delete sequences are not working. In this case le is linked with /usr/lib/libncurses.5.4.dylib.
When I install a third party version of Curses by brew install ncurses and force cmake to use it, everything works correctly. In this case le is linked with /usr/local/opt/ncurses/lib/libncursesw.6.dylib.
I will try to figure out what's wrong with native Curses on MacOS. I don't think it's bad. Most probable LE somehow uses it incorrectly.