Thanks for joining the search - I couldn´t find anything useful either.
FYI - the Yogscast Jingle Jam actually only contained a time limited Closed Beta key (https://steamcommunity.com/app/759510/), given away as a sort of Demo before EA release in March 2020. Those keys are worthless now as that Beta is shutdown for good and not playable anymore. Unfortunately they are still around on the "grey" market sometimes..
But to the best of my knowledge even there the game hardly ever went under € 10,- before the Humble Bundle, now prices seem to be down.
No idea where that mixup comes from. Even now the game should at least give reduced CV.

??
maybe you wanted to reply to the post before mine ?

Imo it´s mostly about the single player campaign : )
MP, as I understand it, is mostly there to add flavour - you can play co-op and choose to have fights with other players during your campaign, all of which you could opt out completely last time I played!
What I find interesting is that the 3 factions really play completely different, so there´s that for replayabilty.
Also they offer a great demo, where you can unlock an item should you buy the game later. (I spent 10h+ just there to get it) ; )