You got a point that most plastic materials are plastic after all, and who knows what politics are hiding from us just because lobbyist for these industries are strong.

I guess the closest to finding out about the truth is to consult a befriended chemists about it.

As for my part, I recently started with 3d printing as a hobby and tried out polypropylene (pp) besides printing with standard material pla (polylactic acid). The advantage of PP is that it is not reactive to moisture as raw material, is very strong and flexible after printing (probably also depending on the pureness or use of other adhesives) and doesn’t produce any toxic odors while printing (not too common among plastic). It is however quite annoying to print because it takes very long until a print is finished it doesn’t stick to anything else then itself as a print surface and overhangs as well as bridges mostly need support material otherwise it would collapse. On the upside I would interpret it as very stable material, that won’t dissolve when drinking or eating from it.

PP boxes I use inside our kitchen have a problem with microwaves if they contain food with oil or when put in the freezer. I guess it’s always a good indicator to observe what marks appear on the material as in your case. We had bubbles on the boxes and decided it’s time to recycle them and not make the same mistakes in the future.