Yeh I agree excluding autosaves is needed, the current code in https://support.advancedcustomfields.com/forums/topic/update-to-wp-5-9-1-breaks-media-selection/#post-152581 should solve that issue.
I had concerns disabling autosave preloading would break autosaves altogether, but it seems WordPress doesn’t dynamically load anything into the editor from an autosave anyway – it only redirects you over to the autosave URL; so there shouldn’t be any issues removing the preloads.
