BB pulls the other DF energy inside of the DF user, not the user.
At best they can stop the random Darkness AoE attack, not the one that pulls the DF energy from the users body.
And even Darkness AoE pull is much more powerful than Law's shambles ability, so its not really comparable, Darkness AoE pulls even light.
DF to DF, creates a connection. Using Haki to suppress the other DF affect on his main body will be irrelevant. Darkness simply reveals the real body.
Thats not like some DF technique similar to Shambles or Disease to negate via Haki.
Simply put: Darkness effects the DF power, not the users main body like Shambles and Disease.
Two different things.
Thats also saying like Kaido's or Big mom's Haki could cancel Law, Kid and Luffy's DF attacks, they clearly couldn't.
Big mom could stop Law's shambles due to her Haki, but not the other techniques.