My internal editor every time I think I've outlined this bleepin' novel.
@Annalee IMO, the proper rebuttal to this is, "Your FACE is a third act!" 😜
@Annalee Three act structure is a critical tool used to deconstruct novels after publication.
If you have start-problem-reaction-problem-reaction.../...-change then that's a satisfying arc; you don't need to bind yourself to the strictures of Aristotelian form and the prescriptive theories that grew from it to have a "valid" book.