Here’s A Strange One

Noticed whilst out last night at the Barton Bike Meet a line on both front and rear tyres. On the front it’s dead centre for the full circumference, the rear is a little offset but again follows the full circumference. You can feel it with your fingernail, but there’s no gap - like it’s a hard line if that makes sense. These tyres were fitted last September but only done maybe 400 miles. The lines weren't visible when fitted for sure, but I can’t hand on heart say when they started to show. I don’t think it can be more than 50 miles ago as when it’s being locked up in the shed and I’m threading the chain through the back wheel the tread is facing me.
I’ve gone back to my tyre guy (who’s been a biker all his life) and he said it’s a new one on him. He said not to be over concerned as there’s no separation, delamination or blistering but is taking it up with Michelins tech people.
Anyone else seen something like this (FYI these are Road 5’s on my 2013 plate Tiger 1050 SE)

 

Many thanks for the quick response - I knew someone on here would have the answer. Don’t know how new a thing this is, as there was no such line on the previous set of Road 5’s these replaced

EDIT - well I’m an unobservant git . I’ve just looked back and found photos of when I first got the Tiger and there were lines on the near new Road 5’s it had then