I'm sorry, My responses are limited. You must ask the right questions.
...And so as long as men die, Liberty will never perish.
Why is Harry surprised to see Goodman Grey transform into a racehorse when he's already seen Injun Joe transform into a bear the size of a minibus back in Turncoat? Is this just an oopsie due to Jim losing track of what happened during which draft of Turncoat?
Not every word JB rights is a conspiracy. Sometimes, he's just telling a story.
Did Harry know he could do more than just change into other people? I could easily imagine him thinking Grey is just a one trick pony who can only go from human to human rather than having the whole animal kingdom available.
just a little while before the change into the horse, Harry had seen Grey change into animalistic shapes during his fight in the vault.
I think the alphas transform into a kind of dire wolf, the huge bear a type of dire or Kodak bear. When they change they add mass from the never never to assume an animal form.