Arcade Documentation: Arcade FeatureSets / related FCs

[Bud]

The FeatureSets section in Arcade developer documentation seems a bit misleading.
It suggests that a FC needs to be in a map service or feature service in order to use it as a related FC in an Arcade expression:

FeatureSets allow you to access features from feature service layers within the map or feature service.

If I understand correctly, a FC doesn't need to be in a map or feature service in order to use it as a related FC in Arcade:
Arcade: Use related FCs without needing feature service

Could the developer documentation be changed to make the above more obvious?
Thanks!