Difference between a Magus Variant, and a Skeletal Champion variant

So, while looking through the template options for skeletons and animate dead, one of the listed options is the magus.

Magus: These variant skeletal champions and zombie lords are minor spellcasters (typically 5th-level or less) that have retained both their intelligence and their spellcasting abilities. Magus skeletons and zombies gain Silent Spell as a bonus feat. (CR +1 plus caster level)

This variant is the only one without an example. Looking at it, it seems pretty abstract. It looks like it may even be argued to fall under Create Undead instead of animate dead. However Create undead has the Skeletal champion template, which already retains class levels and intelligence and even gives extra HD that the magus doesnt seem to.

My question is, which spell creates a Magus skeleton, and if it is create undead, are they basically an extra free feat for the champion? If its animate undead, are they mostly mindless save for their spell casting ability? What is retained?