Broly's not in a position to exploit Hatchiyack's overreliance on Revenger Cannon - Hatchiyack can cancel his charge early if Broly tries to attack him during it, and Broly's not strong enough to win a beam struggle like the Z-Fighters collectively did.
In regular combat it would initially be more even - if Hatchiyack only "might" be stronger than Broly, their power is probably comparable - until Hatchiyack transforms, at which point it'd be all over for Broly.
(Hatchiyack isn't a movie character so, even if Koyama's statement were in any way credible, it wouldn't apply to him anyway)