Font size is definitely not useless. The article assumes that it is, because not all displays are the same size or have identical ppi. However, you are meant to calibrate your scaling settings for typography so that a size 32 font will look identical in any calibrated display or on printed paper.

If you don’t care about printed typography, you don’t need to bother with any of that.

This makes me feel better about my if…then…else walls.