Sounds a bit like an Overton window issue: the Hammer Horror movies were rated R by and large, not PG-13 (though there wasn't a PG-13 I'm their heyday, they would probably not qualify for PG-13 today). Any WotC approach to Horror is going to be more Benedict Cumberbatch's Doctor Strange than any R rated stuff. Think Goosebumps, not Hammer. Think classic Universal Horror (which mostly passed the Hayes Code, which would mean G now), not modern R rated horror.
You keep saying Disney like that means PG, but Disney is the current master of PG-13: and yes, thst is the tone WotC is going for, be ause that is what sells to their core market. The three biggest films of all time are PG-13 movies from Disney.