Looks illegal to me. Ball was outside the tackle box so below the waist blocks have to come from front even for linemen which that wasn't. Defender was clearly running parallel to the line well before the block was made, so it wasn't just turning at the last moment, and the block came from the side of him.
To be outside of 10-2, you’d have to argue the defender was facing the sideline - ie, he gets hit from 9am - sideways. There’s simply no reason that a defender should be facing the sideline on that play. When you’re taking an angle, you’re always watching the ball carrier as you converge, meaning their is an angle. Maybe it’s 9:55am and it’s illegal, but I still hate Refs.
If you hit pause at the time of the tackle, it looks like it’s 9am, directly from the side. So you have to ask yourself why in the hell as a defender you’d pivot and start to turn away from the guy blocking you. That’s dangerous. It reminds me of all the Clemson DL that hold our OL all the time and then they get cut blocked and cry about a chop block. It’s dangerous to play that way.