Lol.
These bags are called cooking bags for a reason. They're want for cooking with. They have all types of safety certifications.
Parchment is able to handle such high temperature liquid heat?
Your cholent doesn't at all taste like parchament paper?
a. Fact is that the water is discolored because of seepage. Its not dangerous, but you are consuming plastic. I guess its a matter of taste.
b. Parchment/baking paper is designed for baking at over 450 degrees. Since paper never melts, (it can only burn), there is no risk of melting. Besides, I would imagine that paper is made of more natural materials than plastic...