When using a sub anim instance, the instance will continue to update/evaluate even when its value is not currently contributing to the final pose.
Open an animation BP and add a sub/linked anim instance to a blend by bool node.
In the sub instance's event graph, print on update or post evaluate events.
In the parent ABP, toggle the blend by bool value.
Expected: When the sub instance is switched off by the blend node, the sub instance should not update/evaluate.
Result: The sub instance always updates/evaluates.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-83410 in the post.