Regular arrows turn to fire arrows when fired at dragon

What I expected to happen was...:
When I fired arrows with an un-enchanted bow at the dragon while it was perching they should bounce off it as a regular arrow

What actually happened was...:
When I shot the arrows with the un-enchanted bow at the dragon they bounced off of it but as fire arrows (like the ones you get when you have the flame enchant on your bow) and then disappeared after hitting the ground

Steps to Reproduce:
1. Give yourself an un-enchanted bow with regular arrows
2. Go to the End Dimension and wait for the dragon to perch
3. Shoot arrows at the dragon while it's perched and they become fire arrows that disappear after landing on the ground