The name for the "cooldown group" does not follow the usual snake_case format, and is different to what is written in the changelog.

Steps to Reproduce:

Run these commands to give yourself 2 goat horns with some unique cooldown group attempted to be applied, and another with its default cooldown group.

give @s goat_horn[use_cooldown={seconds:1,cooldown_group:"custom"},item_name='"cooldown_group"']

give @s goat_horn[use_cooldown={seconds:1,cooldownGroup:"custom"},item_name='"cooldownGroup"']

give @s goat_horn

Play each one.

Observed Result:

• When playing either the normal Goat Horn or the "cooldown_group" goat horn, both have cooldowns applied to them at the same time.
• When playing the "cooldownGroup" goat horn, only that one has its cooldown applied.

Expected Result:

• When playing either the normal Goat Horn or the "cooldownGroup" goat horn, both have cooldowns applied to them at the same time.
• When playing the "cooldown_group" goat horn, only that one has its cooldown applied.

The command that uses cooldown_group should work and the command that uses cooldownGroup should not.