For a ship that has sailed, it keeps coming back into port.
The WADA Code allowed the AIU to make statistical arguments about a national population rarely testing positive from pork during normal times which may not be applicable in exceptional cases, i.e. global supply issues during a pandemic, and for that matter, may not be wholly truthful or factual.
Shelby claimed that pork ingestion was the most likely source, and this claim remains essentially undisputed by the World Athletics, by the AIU, by the CAS and by the Swiss Courts. The CAS simply ruled that she couldn't prove the source to the burden specified by the WADA Code. No alternative source was found to be more likely.
Tygart is right that the WADA Code railroads athletes to 4-year bans, by removing any benefit of the doubt and treating athletes who do not know how they tested positive the same as intentional cheaters.