Here is a card with the plastic inside the holder.
I am sure PSA has given the potential damage some thought. They have cards that are in the millions in their holders.
The first card I ever cracked out was an Andre The Giant BGS 9 and was panicked when I saw the sleeve with the Andre warping inside the holder. Fortunately I got it out before there was any damage to the card. It now sits in a PSA 8 holder. NONE of the Andre BGS 9's will cross to PSA.