No. It is not. I’ve watched the scene a dozen times. His palm is in… facing him, and thumb is in. Even in the screenshot I posted his palm is in.

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.

The thing is… the Vulcan salute is palm out. He has palm in, thumb in. It caught me off guard which was why I felt the need to come post as I couldn’t find it anywhere online.

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