If you are in gamemode 1 or creative you have enchanted arrows in your inventory and you use a bow and it selects the enchanted arrows then they are used up.

I expected the arrows to not be used up as I was in gamemode 1 and normal arrows aren't used up in gamemode 1

To replicate get some enchanted arrows go into gamemode 1 get a bow. Start firing arrows and you'll notice that the amount of arrows goes down.