The article is postulating only a theory. We have seen the opposite true in credit card forms where users have to input card expiry date. No matter what sort of formatting we did, users always typed expiry wrong and our JS would point it out. We finally had to abandon input text boxes in favor of select boxes for card expiry month & year. We measured the eventual success rate and that turned out to be higher as well.

My guess is that since the scope is so narrow (1 out of 12 choices for month) and selection is very obvious, perhaps people made lesser mistakes here. Select boxes are more effective in mobiles as typing takes more effort than tapping.