It doesn't need to be detached to cause a reading that match fdr. Just split shaftwill do. Murphy is lazy.
I find it a impossible coincidence to have a bird strike exactly at maximum gs. Torque at the shaft is maximum at maximum g, so it looks more plausible unless we have other clues (mention of birds cvr) which I ignore.
Finding the vane and the bird wouldn't be easy either, their absence from runway doesn't prove anything, they had a bit of height and speed by then, it could have landed quite far.