Accordingly aid organizer It's not like that at all. I'm very certain that BPAs aren't present in name-brand zip-seal bags, but this is more of a structural than chemical problem.
These bags' zippers, regardless of whether they are single, double, triple, or more, are not made to provide a complete seal. There is probably not much thermodynamic activity in the freezer, but it may be enough to keep the air out for a long time.
The opposite is true when placed in a kettle of hot water. The molecules in the bag and the pot start crashing into one another as the temperature rises. You could get lucky and the seal will stay put. Something on the bag could break, releasing its contents into the sea if you're unlucky.
Furthermore, there is a significant risk of the plastic melting if it comes into contact with the hot metal of the pot. Totally messed up another time. Sous vide cooking eliminates this risk (there are no hot spots), but if the seal breaks, the food could contaminate the water.