The chorus fruit cooldown indicator bar appears to have its maximum height set based on the default cooldown time rather than the time for the current cooldown. This can be seen by creating a custom item with the "chorusfruit" cooldown_type but a different cooldown time than the default (20).
A custom item with the following behavior entity json definition file:
- Give yourself multiple custom items and put them on the hotbar
- Give yourself multiple chorus fruit and put them on the hotbar