The reason why I think the boa losing her DF part is fake is because Lance said some part of these spoilers are fake, but we know that the Koby, Turning to stone, Rayleigh, Yamato, Bounties and macro part are all true. So it leads me to believe that Boa just simply had her fruit negated, and cant use it against blackbeard and right before he can take it, rayleigh stops them