I think the change was forced due to to supply chain issues, rather than an elected change. It seems a bit coincidental it happened a short while after the conflict in Ukraine erupted (or escalated strictly speaking, after Crimea in 2014). The movement to the 02S from earlier "fabric" bellows seems logical as it meant you could have bedding against the bellows and it would stay dry, but the move to the 03S I think was forced. My guess is a new supplier had to be found, they were given a design brief but either didn't have access to the same materials or for their own manufacturing reasons had to use different materials; clearly R&D was lacking (probably due to immense pressure from VW to get stock flowing PDQ) and from that point they've repeatedly been on the back foot.
My guess is as you say, it either represents those that have been sample checked, or they don't adhere very well and half of them fall off.
I think it's pretty straightforward really; pretty much everyone at VW (both dealers and EO) are now saying "if it leaks, bring it in", mirroring pretty much the approach for anything else warranty related. If instead the customer elects to "solve the problem themselves", it is quite clear those affected components are potentially no longer covered by warranty. Now, if VW were being more obtuse with their attitude towards warranty and repairs, I'd be more inclined to kick up a fuss, but as they're being fairly helpful in the main, I don't think their stance is unreasonable.
