When I say The Hobbit, I mean the book. That's lore.
Again, nothing in The Hobbit indicated that Beorn had to "hulk out" to take bear-form or that he has to flip forms all the time. That was purely a game design contrivance that I'm much happier without, although I will otherwise note SSG's usual attention to detail in choosing the term wrath:
"But even with the Eagles they were still outnumbered. In that last hour Beorn himself had appeared—no one knew how or from where. He came alone, and in bear’s shape; and he seemed to have grown almost to giant-size in his wrath."
--Tolkien, J.R.R.. The Hobbit (Lord of the Rings) (p. 291). Houghton Mifflin Harcourt. Kindle Edition.