It was used when I bought it, and the roof had never been coated,.. looked just like you describe. I never coated it, and 8 years later, the roof looked just like you describe. The new owner, who knew these rubber roofs well, was impressed w/ how good it looked, and that it had never been coated.
From all that, I concluded that these roofs are supposed to look just as you describe.
I was always worried about tree branches hurting it because it looked so fragile, so I always carried Eternabond tape. Darned if I never was able to even try the tape,....still a sealed package in my current RV.
Wash the roof now and then,....quit worryin about it.
