Villager Selling two Novice Items

I am trading with villagers to make an epic villager trading area. When I gave a villager a grindstone to become a weapon smith and it pops up with coal for emerald and emerald for axe and emerald for sword. I have never had this happen with any other villager being able to sell two items in one area. I assume this is normal and even with turning to zombie villager and back didn't change anything.