The answer is correct but there was a tweak of this rule several years ago. If the "B" player jumps, catches the ball and then lands on the sideline, it is not a foul for free kick OOB. The ball belongs to "B" at that spot.
Again, terminology is important. He doesn't 'catch' the ball in your scenario. Since he landed on the sideline, he didn't complete the catch. But, since he was, officially, inbounds when he touched the ball, that eliminates the possibility of a foul for a free kick out of bounds.
In those situations, I suggest using the terminology "secure," "secures," "secured," as distinct from a defined 'catch.'
Indeed, that was changed that some years ago. Prior that, a B player could be airborne, secure and carry, or bat/muff the ball out of bounds, and that would have yielded a foul for an illegal kick OB. (Honestly, can't remember if Adams did that, or Redding - it has been that long ago).