I'm not picking Manny. I simply cannot see it. And anyone who really analyzed the Lucas, Horn and Broner fights will see it too. It's always been the case though.
There are two things that Manny Pacquiao can't deal with: a high, accurate work rate (Morales 1, Bradley II, three of the four Marquez fights, Horn) meaning a guy who isn't afraid to take risks and throw on him, and a fighter that moves as well as or better than him (Bradley, Marquez, Mayweather).
Manny Pacquiao looks absolutely stellar against guys who (A) stand in front of him (Clottey, Oscar, Barrera, Margacheato, Rios, Cotto, Hatton) and/or (B) who are afraid to take real risks and throw on him (Broner, Mosley, Lucas, Algieri).
Manny Pacquiao throws the same pre-set punch in hopes to nail a combo of 3-4 of that first shot. Horn showed the blueprint to nullifying it by moving to the side whether Manny lands that shot or not, then you see Manny continue like a robot in the old direction with the other punches and can counter him.
Keith Thurman is taller, rangier and uses those in every fight he's in. He's not afraid to go to war, but he's a smart mover and that was on full display against Lopez despite him getting hit.
The only outcomes I see, as I said, are (A) a controversial draw to set up a rematch, where one guy clearly won, or (B) a Thurman decision.
You have some good points, but it's nothing new. Thurman win by decision because it make more sense to keep him undefeated. Win or loss Manny is still a big draw for PBC, it's really that simple.