Checking the Run Physics with No Controller box in an animation Blueprint causes the Mannequin to change over to the "In Air" animation state. This will only occur after making the change then compiling and reopening the asset.
Results: The Mannequin is now in the "In Air" animation.
Expected: The Mannequin should stay in the idle animation as before.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-74512 in the post.