Here's the issue, Freedom Breeder bought a lot of their stock from Dan Wolfe when he retired. A lot of that stock was arroyo and possible arroyo stuff. I saw Dan's collection in person while he was still in business in Montana. I saw his pastel arroyos, pastel rios, along with a bunch of his other projects that have since stalled (nova, black lace, quake, some dinker stuff). Dan Wolfe was the originator of arroyo/rio, his channel is still on YouTube for reference but hasn't (understandably) been updated for years. I have an arroyo female straight from Dan because there was so much misidentification going on and I didn't trust anyone else but him.
I'm not doubting you, I'm doubting Freedom Breeder. Regardless of how this was listed and sold as, I don't see arroyo in that animal, not even a tiny bit. I'm surprised they sold it as such. If the animal was in my possession I would hesitate even calling it a possible arroyo simply because it's not expressing any of that gene at all.
Here is Dan Wolfe's video explaining what arroyo/rio does, notice the dorsal stripe in every single combo he brings out.
https://www.youtube.com/watch?v=eSubcLxWTGc