These statements are problematic. Agito is mystical or it isn't. It's really not logical to say that Agito isn't mystical even though the thing that creates Agito is mystical.
If the Seed of Agito is mystical, then it makes sense to say the evolutions it causes are still a basically mystical process. For Agito to be truly "organic" like, say, Shin, I think there would need to be no magic involved in the process whatsoever.
(And yeah, I'm aware I'm arguing that, say, Amazon would be mystical by this argument. But why not? He's created by a mystic bracelet, how could he not be mystical?)
Like I said, I don't want to say anyone's wrong. It's just that, let's say, you insert a twenty bill into a vending machine. You're still able to get a coke, same goes with a ten bill.
I guess what I'm trying is, despite it's different creation techniques, the end result is the same. That the body changes. Biologically, it changes. Headaches, pains, and supernatural abilities (enhanced human abilities like being a telepath) are the proofs. I mean, it's like taking a drug. It affects your body, causes reactions to it. Is it chemical changes? Yes. It affects parts of the body and may cause them to change. Is that biological? Yes.
I guess it's safe to say that, either way, Agito should be considered an Organic Rider, much like Gills, Kuuga, and Chalice.
The Seed of Agito itself may be mystical, but the result is an organic Rider. Input doesn't always result the same way as an output. In some cases, yes.
Yes, he is, in a way, a type of mystical Rider, but overall, he's more organic and should be classified that way.