Brulee didn't help Luffy...Luffy used Brulee to escape....you take manga saying it is not 1 vs 1 but Oda said Luffy defeated Katakuri not that Luffy defeated Katakuri with Brulee help..the same way when Doflamingo was defeated, it was attributed to both Luffy and Law.....
Luffy lost his fight against Katakuri. Then ran away, would've died otherwise.
Then they started fighting against. And then the bitch sister interfered heavily, resulting in Luffy getting a wound and then Katakuri, who wasn't much injured up until that point, stabbing himself and setting himself on timer, too.
I won't call a fight with so much outside interference influencing the result a 1v1