Yes. As I said in my post, I emailed GB, everything I found, including the member links to both the shill and the seller.
I just did a search back through my emails, I actually emailed them twice in May 2021, and I did get an automated reply from GB. And looking at the shill's feedback it shows only one purchase/feedback right after my emails, and the seller's feedbacks slowed down a month or so later (the shill had never left a single feedback). The seller, with over 400 total feedbacks, only has single feedback this year back in March and has no current auctions, so maybe GB did act, and just never contacted me back.
I doubt the shill paid anything, but assumed the seller was paying GB their commission, although I don't know exactly how it works if a seller relists an item.
I figured it most likely worked to their advantage or they wouldn't have continued doing it. The 29 auctions that the shill "won" were the times he didn't get out soon enough; there was no way of knowing how many times he successfully drove up the price and then stopped bidding. But the recent feedbacks the seller had received, where you could still view the item and the bid history, the shill had been a bidder on everything viewable.