When a player is outside of the world border, you can't really do anything and when trying to keep on moving you will realize there is an invisible border that stops the player from wandering even farther, but when trying to shoot an arrow using the bow it can go through the invisible world border that's outside the world border.

How to reproduce

1-Start by teleporting outside the world border using this command:

/tp 29999999 256 29999999

2-Then obtain a bow and an arrow and use the bow against the border.

3-You will realize that arrows can go through the invisible border.

Observations: Arrows can go through invisible border.

Expectations: Nothing (including arrows) can go through the border and the bow cannot be used outside the world border since you can't do anything outside the world border.