When I bought my first trailer about 20 years ago, I fell for the "protection" spray for the interior fabric areas. The said that it would protect against any spilled liquid and prevent stains on the fabric. While waiting for it to be done, I thought about it and realized that I had been scammed.
When they said it was done, I got a cup of water and asked the salesman to come to the trailer with me. I poured a few drops of water in several locations and some beaded but most were absorbed.
Told the salesman that I would not pay for it and they deducted it from the cost.
Win-Win for me.