Apple does some clever tricks, like artificially slowing down the guess rate if you have enough failed attempts. This feature led to whole FBI vs. Apple standoff over the San Bernadino shooter's iPhone.

Once stolen, somebody can always factory reset your phone. The sorts of bypasses you linked to are exactly the sort of thing that Apple and others occasionally bump into and work diligently to fix. This is in part why it's so important to install security updates regularly, since they will address all sorts of things like this.