The iron ore to steel direct recipe does not allow adding productivity modules, even though the vanilla ore to plate and plate to steel recipes both support adding productivity modules (and now that I think about it having 2 steps both of which are boosted with productivity modules is still better than a single recipe boosted by productivity modules, so I guess it should be a tradeoff between bonuses and convenience)

I have seen another 1 year old thread that mentions this, but that thread talks about bob's modules, and the dev reply mentions a setting in bob's mods that allegedly should help, but I just installed bob's modules and it didn't help either