It is "unit_set_to_unit_junctions_tables", it doesn't need to specify dwarf units or specific namned units, as you can see in the other columns, "Unit Caste" have associated "melee_infantry", "missile_infantry" and "monstrous_infantry". That means any unit that have the "Caste" (look in db/main_units_tables) as any of the three mentioned would benefit from the "wh_main_effect_force_army_campaign_recruitment_cost_infantry", no mather the faction or culture.

So any infantry, if you have this technology, would have recruiment cost manipulated.

My god, I could’ve just asked for advice five hours of searching earlier — thank you so much.