well that DF things is obviously not true but the part yes.. u can say thay the drug gave him his emotion back in a way.. hence giving him access ti diable jambe.. and yes its a technique like Kinnemon's.. zoor did it with a sword just like Kinnemon.. the reason why they can summon flames is due to their spirit.. also and explanation to zoro's ashura.. i'd recommend u searching more about this
Foza, doffy, hyogoro, marigold, luffy, kinemo, zoro, katakuri, hannyabal, king, sanji, who am I forgetting? The fire powers are definitely spirit or haki related at this point. The idea of Diable jambe being a vinsmoke related power should die in a fire 🔥