Yeah it is a fake pet, as i stated, it is a pet but it doesnt work as one, by their own words:
Whatever you say to make you feel right i guess.
Specializing is not throwing away stuff that should be part of your basic toolkit
Imagine if Prot warriors and paladins, to “specialize” in tanking bliz removes the option for then to to use weapons? only shields? you would have clowns saying: “If YoU wAnT wEaPoNs Go PlAy FuRy/aRmS” "weapons isn’t part of prot fantasy and theme’’
Shadow priests still use holy abilities, even when they are specialized in shadow magic, they can still heal, shield and use other healing abilities
Removing pets from MM entirely would be like removing any holy skill from shadow.