Unless i'm reading it wrong, dosen't the spoiler say that it was Sabo who taught Robin CoA during the timeskip??
Nah he teach her his shockwave Dragon attacks not haki.
She gain fight skills but not haki from her Revo training.
As I said Luffy said that only he,Zoro and Sanji could use haki during Punk hazard with literally confirm that Robin didn't have it. Later Robin couldn't hurt Monet because she didn't have haki. Robin had clearly not haki after the ts. She learn it most like after DR. And 2months already pass since DR. That is a big timeframe in one piece world.
As Zoro said, the strawhats massive grow up from each arc. Current Robin is a whole new lvl then her version in Punk hazard or DR. She would stomp now Monet or even Doffy top members.