Or… maybe it’s not. Gene Roddenberry was alive and on set for majority of TNG’s season one filming. He would have noticed such a mistake.

Another fascinating point is it’s not tradition to do the Vulcan salute to a non-Vulcan of which none of the characters on screen were so it’s strange he’d use that salute when not referencing anything Vulcan in the scene.

It’s not though. I’ve seen ALL Star Trek series and am pretty well versed so when I saw Riker make that hand sign and it’s the reverse of the Vulcan salute with the thumb tucked in it brought me to post. Even the wiki says the Vulcan salute is palm out, thumb extended.

Here’s a link to the photo: https://ibb.co/C7sshPL