The bug

Jumping and throwing/shooting any kind of projectile causes it to spawn with the player's velocity. Expected behavior is to have the projectile's motion only based on the rotation.

How to reproduce

Place a repeating powered command block with the following command:

/execute at @e[type=snowball] run summon armor_stand ~ ~6 ~ {NoGravity:1}

Then, jump three times and throw the snowball at different times in the jump. Throw it when you are going upwards, then when you are at the peak of the jump, and one finally when going down.

Looking at the trajectories (see screenshot) shows the difference in where the snowball ends up.