It's not fake unfortunately. Many many more got revealed that look equally as ridiculous as this... thing.
It is fake. If it isn't here: https://www.serebii.net/swordshield/galarpokedex.shtml then it wasn't officially revealed nor confirmed and it is fake. Simple as that.
Ever heard of leaks? Ya'know, these things that aren't yet officially revealed, thus not 100% confirmed but often not 100% false either ?