The collection method the way it’s described prevents it from coming into contact with air (just water), but you bring up an excellent point I hadn’t considered, which is that maybe millions of years of farts are to blame for the current state of things
Not awful. I’ve had only positive experiences. No buyer protections, but it’s hard to get scammed buying something in person from someone local, unless you get it home before realizing it’s fake/broken, or they kidnap you and lock you in their basement. There are pretty simple precautions you can take against either, not that there’s any foolproof solution…but I wouldn’t say awful.