Yeah I think this it - it’s to accommodate companions; technically the ability is not on a card in your actual deck/battlefield (making Rule 10 not applicable?) but an extra deck mechanic like Un-set contraptions, stickers etc. (although I do not know how “assemble a contraption” works on the one legal contraption card?).
EDIT: Also the inclusion of “traditional card(s)” probably gives companion wriggle room.
I’m not really adding to the conversation with this but wanted to share anyway: