I mean no disrespect Chief, but I had to run a 14T/47T on my bike for a little bit because a company sent me the wrong sprocket, so I ran my wheel all the way back on the adjuster (So I can add a larger front sprocket and not have to add links), and between the forward setting, and the rear setting, I really felt no difference with the handling/turning of my bike on the street.
I've never ridden on the track (Hope to change that this upcoming year), and I definitely am not educated in how stuff works like wheel adjustment, but just from personal street experience, I don't see how it could affect him to where it's noticeable.
Then you've never leaned the bike long enough to miss an apex, etc. When you've hit 1 turn 50 times, and then you move your axle well over an inch, then you go for time 51, you will be wide, off the apex, or the bike will turn differently. On the 3rd Gen, I've been all the way forward and back. All the way forward and it's a tank slap monster and nearly uncontrollable over bumps on the street.
If you're just cruisin around town, no you won't notice much of anything. But move that axle an inch and it's the difference between lifting the tire and not in most instances on the 3rd gen.
You setup a Gen 1 very long and tall in the front, and you get a TON of squat on the shock. It's insane, and the bike is long to begin with in regards to forks to accomplish the wheelbase, etc and it's a shitty setup.
It only takes a couple mm's of adjustment on the bike whether it be ride height, or sag and the bike acts much different. Maybe not to you, but to someone who's riding the edge of the tire, scrounging for tenths, it really makes a difference.
If he just had the Chain installed is it possible that they adjusted the chain TOO tight causing the suspension to bind up and loose grip when it unload a little? Happens on the track if your chain is very tight and not allowing the suspension itself to work properly and keep the tire in contact with the pavement.
Not my diagnosis but food for thought.
This could be the best explanation yet. The OP could be getting ANTI-squat, vs excessive squat that I would expect since it's so tight. A very tight chain can hinder the suspension travel in the rear, chip sprocket teeth, and make tight spots in chains, etc..
Maybe the OP will return so we don't need to keep wondering what to debate over.