I just changed the GP4000 rear tire today.
It is the 25c with the reflective side wall.
The tread was almost completely worn and I would have left it on longer but we are starting a tour on Saturday.
I looked at the bead and there is exposed fabric around the entire tire.
The new tire has rubber or whatever it is covering the fabric.
I think it is normal for the rubber to wear off exposing the fabric and I don't believe this is an indicator that the tire will blow off.