Hi,
"Every Frame" is about telling the action that the process needs to be repeated over time, then it's up to each action to define how it will be implemented, most will use Update, some will use different functions like FixedUpdate, or LateUpdate.
I guess, the ideal way to go about this is for actions to provide a new way to define "every update" with *ALWAYS" the choice to define when ( update, late or fixed or OnAnimatorIK and OnAnimatorMove). This would then be something that can be spreaded across all actions, and be something users are acquainted and used to on a general level. The downside it of course the initial "what's this...", so maybe an everyframe action interface with a "+" to reveal more to not scare the user away when nothing special needs to be done.
Bye,
Jean