There was a bf movie at theatres in the late 70's, early 80's that featured that particular footage as the kickoff point. Pretty much as rock solid evidence according to the movies director. Then the rest of it was castings, unconfirmed eyewitness accounts taken years later and some other blurry footage from unknown sources for the most part.
Yes, that is the footage I recall. There were extensive bits with Patterson trying to explain what he filmed despite the horse moving so much it made it difficult for anything to be clearly seen.
I do know that by the 90's only enhanced stills and short clips taken from that footage were used on the then popular woo tv genre.
Other sources had created clearer, maybe better "evidence" that became the meat of the genre.
I grew up watching illusionist, magician shows every chance we got and learned early on the truth was usually in the missing details nobody was telling, if not actively making effort to hide them.
I took that same vision into the woo tv/paranormal tv realm and it became clear they forgot to mention where, when, whom or most other vital information that would cast doubts on the story they wanted to sell.
It also became obvious that deep woods, wilderness areas in general were barely accessible areas on the shows. But could be easily accessible by boat or roads somehow anyway.