Most of the dry erase films are polypropylene. I am not familiar with the WYPET product. The specs say it is a vinyl, but goes no further in regards to the coating or adhesive. Since it is for indoors only, I assume it has a polypropylene coating of some sort.The dry erase ability is just inherent in the material. The ones that are not polypropylene are chemically coated or are manufactured from a very different material. Straight vinyl is not dry erasable nor is plain polyester (although I know several people that sell it on their maps as dry erase laminate) short term yes...long term no.. polypropylene will also yellow over time...faster if it is in direct sunlight. There is one exceptional product, but it is cost prohibitive,
Seal Graffitti Free laminate..$800 per roll but it works outdoors for 5-7 years. It can be written on with a PERMANENT marker, then wiped off like dry erase...there is also another thermal dry erase film that has a polyester base, with a chemical coating to make it dry erase. No ghosting.
good luck. Information is always or it (should be) free.