I've got a 2021 MYP and the aero shields for front and rear are all a thick plastic (Looks like either ABS or PP to me, couldnt see die marks with material identification without lifting the car). The rear one was knocked loose last week when I was driving in the rain. It buckled and folded back, making a horrific noise. I was able to (in the rain) manage to get it unfolded and enough back into position to get home driving slowly. I did a bit of surgery at home to get it stable enough to last until mobile service, which should be today. They are quoting $364 for the repair, crossing fingers that a coffee and pleasant demeanor will help get that waived.
I'm personally not outraged that they would charge for replacement of this, nor that older designs used a felt material. It seems likely that the most common failure would be due to outside factors that would not fall under warranty. Stuff happens and I'm not an automotive engineer with the experience to critique their design choices. The panels that failed on my vehicle certainly seemed remarkably stout (judging by how hard I had to kick them to get them back into position). Building anything involves tradeoffs, otherwise every car would be build from all-titanium and would cost $750,000.