Mark it is kind of you to share all the results of your trials and diligent to undertake them.
I am shocked by the problems you have had and it looks like that horrible aminopyralid is present. So much for farmers (who grow the horses’ hay) honouring the agreement they sign that anything sprayed with AP stays on the farm.
Its tragic that a valuable resource for gardeners has been turned to poison.
Yes I agree that your green waste compost looks good, well done making that comparison.