Do you think that part of the problem is people inspecting the seals?
If the seal has a thin coating of rubber over the central steel clip, surely pulling it on & off is more likely to expose the steel which will then rust.
The tape put on the edge of the roof should stop any rust coming into direct contact with the paintwork as it forms a physical barrier, unless of course the steel clip has scratched through the tape as a result of it being pulled on & off.
If I was pulling the seal off once a year to inspect, I would be thinking about a new seal every time as a precaution.
Inspecting the seal should not cause an issue, the first time I inspected the factory fitted seal it was rusty !
the replacement seal was than found to be rusty after the second inspection
the third seal rusted after two weeks and was visible from the outside !
the amount of rust experienced will simply rise above the tape through natural process
the seal is not a water tight seal against the roof panel, Have you ever looked under a roof seal ?
the answer is there is a lot of crud and water accumulates in the recess, providing an ideal environment for rust to form on a faulty part
I don’t think merely pulling the rubber seal back in two foot sections twice a year causes the issue, I think VW provide sh ite seals that are known to cause a severe issue with their product and are unwilling to fix a problem they created & know fully the consequences (4K repair and a two year wait with no guarantee to fix the problem)
look at the rust carefully, this is after two weeks, the seal has failed on the out side and inside. Had I not requested tape to be applied to the front lip, the rust would be in contact with the roof panel, and bi metal corrosion will start very soon after. the tape is a sticking plaster (literally) it is not applied to the whole roof, you can see from the photo the rust will track along the rubber seal and as it grows it will breach the tape (where it is applied)
this is a case of poor product not fit for purpose.
why are the dealers told by VW via a work shop bulletin, to remove the seal and inspect for corrosion if the action of removing the seal damages the seal seal to the extent the problem would occur ?
The applicable Workshop action is 75A1 states that if the roof frame seal has damage such as corrosion or cracks then it should be replaced. Even if your vehicle is not due the workshop action and the seal has corrosion then it is a warrantable item and should therefore be replaced.