I think they’re getting confused with a similar sign. If you do the peace sign sweeping the fingers upward but with the back of your hand facing the person then that means up yours. Or at least it did when I was younger.

peace sign is forward, up yours is backward. definitely slipped out of australian use in the last few decades at least, but people who were around for the pound might remember.

Kiwi here, same.

I’d find it weird someone is using the term groovy in this day and age, but that’s it.