The marks are created by the feed dogs of the sewing machine.
Close but not quite.
It is the presserfoot that creates those impressions. The feed dogs (or...I suspect...feed wheel in this case) would never be allowed to touch the grain surface of the upper.
But that said, even though it is minor, cosmetic and will disappear with time, I don't think it is universal or even acceptable. Those marks may be the result of the presserfoot tension being set too heavy.
But in any case they could have been boned or ironed out.
'It a stitch marker that is used on bespoke shoes and we like to use it on our bench made to show that we put all aspects of our bespoke into out bench made shoes'
What's that mean?
It's bogus blather...intended to soothe the customer. Don't get me wrong G&G are admirable shoes and the workmanship is, generally speaking, beyond reproach.
But...as so many have pointed out to me....accurate explanations are often long and complicated and, from a corporate POV, it is asking too much of the customer to sit still, much less understand. If the customer was capable of understanding, he wouldn't need to ask. (don't shoot the messenger)
I have noticed my last x3 GG shoes (all Arran boots) all have these track marks running parallel to most seams. I figured it was due to the sewing wheel while the upper was stitched. It is not something I have seen before on my GG shoes, and figured it was just a slight drop in production quality. No other new issues otherwise for me...