Take a small snippet of film and put it into bath A under full light and see if something happens. Does the film develop, maybe only a little bit of blackening? My Diafine usage is some years ago, iirc the dev time in bath A did matter and only bath B is not critical at all because of the complete exhaustion of the remaining developer within maybe 60 seconds. And temperature does matter. Not as much as as with 1-bath developers, but it does matter. And at 80 °F or more I definately got grainier negs.
After my experiances all 2-bath developers already start to develop in bath A, bath B is only a boost. I liked Diafine a lot, but now I prefer a (homemade) 1-shot Xtol-stlye developer. Much better control with dev time and dilution and usable at least up to 80 °F (my room temp during hot summers) with adjusted times, the Ilford chart works fine. There is really no need for another developer than Xtol imho if it wouldn`t be a little bit boring after all. But there is still Caffenol :duckandcover:
Diafine: fire and forget, conveniant, usable, but not the best you can get. My humble opinion, ymmv.