pukunui
Legend
I maintain that's because those traits have no impact on CR.CRAWFORD DOES NOT METION WHAT IMPACT SPECIES TRAITS ADDED TO NPCS HAS ON THE NPCS CR.
However, that being said, having reread the "Creating a Creature" section in the new DMG ... it's clear to me that those guidelines are expressly focused on ways you can tweak a stat block without impacting its CR. In a number of places, it advices against changing something that would impact CR. And to that end, it tells you not to add a trait that confers THP.
Therefore, strictly following the guidelines in the 2024 DMG, if you want to make any of the generic humanoid NPCs in the new MM into an orc NPC, then you would have to not give them the Adrenaline Rush trait.
You can add things like Darkvision, Fey Ancestry, advantage on saves vs being poisoned, and so on because those are specifically called out as not impacting CR.