I don’t recall why Riker would have been using one in that context, though, unless TNG was trying to establish the gesture had expanded in use across the Federation.
EDIT: also, this is in S01E15 “11001001”, not E14.
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.
Nope. His palm is definitely out. He just doesn’t have his thumb extended. Other than the thumb, it’s a completely normal Vulcan salute. Perhaps Frakes had a bit of trouble with it early on and just hadn’t got his thumb out properly yet?