It doesn't mention flexbox[0] either. It's not an in-depth examination, it's blogspam. There are better[1] years-old[2] resources which are no more incomplete.

[0] http://philipwalton.github.io/solved-by-flexbox/demos/vertic...

[1] http://css-tricks.com/centering-in-the-unknown/

[2] http://gtwebdev.com/workshop/vcenter/vcenter-inline-css.php