Are the hit points and proficiencies of a class “class features” for the purposes of spells like Magic Jar and Shapechange?

While you're answering questions, are the hit points and proficiencies of a class "class features" for the purposes of spells like Magic Jar and Shapechange, that say you do/don't get class features?

— Thomas "You Can Call Me Tom" (@thomasabarry1) November 5, 2018

In your class's description, any feature under the "Class Features" heading is a class feature. #DnD https://t.co/NdcIm8xUJP

— Jeremy Crawford (@JeremyECrawford) November 5, 2018