You may be misunderstanding the concern expressed on that page. A button communicates action when activated; a link communicates navigation (not necessarily "load new page", perhaps just "show new information on current screen"). Using a button for navigation
or a link styled like a button for action has potential to thwart these expectations in various ways.
I'll admit, sometimes this makes some sense; you may be building an interaction that doesn't map cleanly onto either "trigger action" or "show information", and you wish to pick and choose the semantics that best fit your needs.
...But then there's the situation you allude to, where you have a button (action) and a link (navigation) and are just trying to make them look the same for consistency. Even if you pull it off visually, the chance that an end-user's client software will misinterpret what you're doing in some way and cause confusion is high.