Bad reffing. Plain and simple. Yapp knew it. FSR couldn't see as he was seated behind Yapp. Ball path makes it obvious. If you slow down the vid to 0.25x speed, you can clearly see the 4 move first...if knowing the physics of the shot isn't enough for you.
Baffles the mind how a professional ref doesn't just think to themselves, "if CB goes this way, good shot, if that way, foul" before the shot is even taken.
Would've been nice to see Yapp call a foul on himself there. I get it, if ref doesn't call it, it's not a foul, and as a player you just take those when it's your turn. I know one thing for certain; Ronnie O'Sullivan would have called it on himself.