Are landscapes severely bugged (extremely blocky shadows until you change component sizes)?

Go and create a landscape and import from a heightmap, then try out the smooth brush. For me, it’s like painting with a color over the polygons. Things end up looking like this:

I’ve tried this across multiple projects.

The only way I’ve found to get rid of this weird behavior is to change component sizes (no need to actually change anything, just press Apply). All shadows will change drastically and the smooth brush will work again.

This is in 4.23.1 by the way.

What’s up with this?