For me, it has a picture where it specifies a “polypropylene container”.
There’s also this bit from near the end of the abstract:
Additionally, the polyethylene-based food pouch released more particles than polypropylene-based plastic containers. Exposure modeling results suggested that the highest estimated daily intake was 20.3 ng/kg·day for infants drinking microwaved water and 22.1 ng/kg·day for toddlers consuming microwaved dairy products from polypropylene containers.
So, they’re, at least, discussing polypropylene and polyethylene.
There’s nothing wrong with OCI Images. If you’re concerned about the security of Docker (which, imo, you should be) there are other container runtimes that don’t have its security tradeoffs (e.g. podman).