Some years ago I happened to visit a friend at the same time the vet was there to give her horse his shots and wormer as friend couldn't get it in his mouth.
The horse was a gypsy cob, thick set and thick in the head.
It was farcical, the horse was throwing both women around as if they were bits of paper.
I offered to give a hand me the female vet said that she could manage.
Twenty minutes later, lots of bruises doled out as the horse smashed into them, no injections or wormer given, they couldn't get a twitch on him either.
The vet said she would be back the next day with help.
As she came out the stable so I walked in. The horse went to barge me so got a good whack with the rope across his chest. I picked up his blanket, threw it over his head so he couldn't see, turned him hard and fast in a couple of circles, told the vet to come in and give the injections and once they were done I administered the wormer with no problem at all.
If they cannot see they don't want to move and although I agree they should be taught to accept, sometimes playing artful, especially if you are on your own and don't know a lot works.
It is far safer than trying to keep their head still by tying hard.