An OSC outsources all of its security incident and event monitoring work to a third-party...

The Scoping Guidance defines Security Protection Assets as systems, tools, or services that provide security functions protecting CUI assets, even if outsourced to third parties.

Extract:

“Security Protection Assets are tools, systems, or services that provide security functionality (e.g., SOC, antivirus, logging) to protect CUI assets. These must be included in scope.”

Therefore, SOC and AV must be categorized as Security Protection Assets.