Originally Posted by
PJim
There's some confusion here. The original Jumpstart launched on July 17th last year, and has the legality you posted, and I've been assuming (presumably correctly) that it's been legal the entire time I've been here. Jumpstart: Historic Horizons is the new set, and doesn't get a physical release, it's an Arena only product. It's legal for Historic, which is a sanctioned format, but not for Legacy and the rest. The gimmick is the card effects that are easily handled in a digital game, but wouldn't work well with physical cards, so it's unlikely they'd ever be legal in paper formats.
I don't personally see a reason to exclude them, as they are real cards for a sanctioned format, and not Un- or otherwise weird cards, and they should work fine in 4CB. But the fact they're not legal in paper formats does make them something different to everything else that's legal.