I think the PB article means to say that the idler is concentric with the pivot. That's what it looks like to me.This PB article says the chain is in line with the pivot.
I'm having trouble envisioning how this pulley placement produces anti-squat... Oh wait...
Sorry typed question too soon, am I correct in thinking that the pulley being above and behind the pivot when pedaling (under sag) would produce anti-squat?
Without having plugged this bike into Linkage, I'm going to guess/estimate some numbers here:
The idler looks to be around 16T.
So, if the bike is also in the 16T cog at the back, then there is zero chain growth contributing to Anti-Squat.
Without chain growth, Anti-Squat is wholly made up of what I call 'Frame Anti-Squat' (which is generated by the upward angle of the swingarm).
In this gear, the chainline is parallel to the swingarm line, and it looks like Anti-Squat will be around 50%.
Also, as the suspensions compresses, Anti-Squat will decrease pretty much linearly. So at sag, it's more likely to be somewhere around 30%AS.
Going to a larger cog at the back will increase anti-squat, and going to a smaller cog will decrease it.
This is the trouble with concentric idler/pivot designs, because there is zero (or minimal) chain growth, then the main pivot needs to be really high (and/or the idler pulley really small) to generate reasonable %AS figures (100%-150%).