I dunno if you would call it a "cult" following, but in reading all the threads here, they do get talked about an awful lot for how long/how many were made.
I liked the 26 inch wheeled road bike idea so much I searched about 6 months for an XO1 & eventually got a custom Rodruguez specced with 26's instead.
Imagine my surprise when I saw an original XO1 for $200 at a swap meet when I hadn't even taken delivery of the Rodriguez yet. Oh, well, C'est la vie.
As far as Grant Peterson, I don't know. But on the cult following thing...a definite maybe.
Edit: Sheldon Brown has an article on the subject.
https://sheldonbrown.com/bridgestone/