It was grouped with a non-classic hotfix. Not sure why they haven’t put it here, it does make it difficult to follow when done this way.
"Season of Discovery
- Boon of Blackfathom no longer applies to pets.
- Developer’s Note: We are essentially removing the ability for pets to get Boon of Blackfathom for now. Now that pets scale with stats, allowing them to get certain world buffs would effectively let them “double dip” on these effects and gain far more damage than intended. We’ll continue to review this as we move through the content phases and make adjustments to how world buffs interact with pets as needed."
WoW Hotfixes - January 2 - #234 by Bornakk
- Developer’s Note: We are essentially removing the ability for pets to get Boon of Blackfathom for now. Now that pets scale with stats, allowing them to get certain world buffs would effectively let them “double dip” on these effects and gain far more damage than intended. We’ll continue to review this as we move through the content phases and make adjustments to how world buffs interact with pets as needed."