I got a notification from google merchant that the feed has an error. The feed had a global issue of authentication failure. I tried fetching the feed again and it failed.
I then set the Super Bot Fight Mode to “Allow” bad bots and then tried fetching the feed again which was successful. So I assumed google merchant was behaving the same in both attempts. If it was using the same IP and the same request then the Super Bot Fight Mode was blocking this request.
Then I did this re-tested several times and had the same results when in “Challenge” google failed and in “Allow” successfull. I am pretty confident Super Bot Fight Mode blocks GM good known bot.