I think this could be true or false, depending on how the world is. It depends on how different the two types are viewed. If people are used to communicating with Kitsune to the point where it's natural and there is no bias against them, there's a good chance they wouldn't react any differently to one at all.
That's completely true; you make a good point. I kind of assumed kitsune were rare based on the fact that you had to choose to morph into it (and only the MC gets the choice if I understood correctly), but if that assumption is wrong, then you wouldn't necessarily need too many different reactions/branches.
I also think making the player make an unknown but important choice is a matter of narrative design. That's a pretty tense decision and it would really mean something in the context of the game if they had to stick with that choice. It could be something that can't be undone for a good reason and the tension from making the choice could add a significant value to the overall game.
I don't think the juice is worth the squeeze. While the dramatic effect is undeniably cool, this "unknown but important choice" drastically changes the way the player goes about playing the game for several hours (or more), in ways that are not all positive. The main problem is that (I assume) the player has no way to know what each play experience will be like at the point they make the decision.
It would be like if a game asked you to pick a class between Borbleebeep, Trararalel, and Kreggamor before starting the game. Even if those classes came with brief descriptions of what stats/abilities they have, the player will have no idea what they'll enjoy more. Except in the Kitsune case, the player will have already invested some amount of time (possibly hours), and unless they've been really smart about keeping multiple saves, there will be no way to back out from a decision that forces them into a playstyle that seems really un-fun (unlike in the "pick a class" scenario where you could just restart the game).
On the other hand, if the player has already gotten to experience both the Human gameplay
and the Kitsune gameplay by this point, a lot of these drawbacks disappear, and the only big thing you need to worry about as a designer is the extra work that goes into branching some or all things from that point onwards, based on the player's choice, if Kitsune aren't normal, common members of society in your world.