According the WHO (the organization that keeps a great list with everything that's definitely carcinogenic):
"Processed meat refers to meat that has been transformed through
salting, curing, fermentation, smoking, or other processes to enhance
flavour or improve preservation. Most processed meats contain pork or
beef, but processed meats may also contain other red meats, poultry,
offal, or meat by-products such as blood."
All the way down there's also a point about the manner of preservation
"24. Different preservation methods could result in the formation of
carcinogens (e.g. N-nitroso compounds), but whether and how much this
contributes to the cancer risk is unknown."
The WHO doesn't go this far, but based on compounds in some processed meat that are carcinogenic by itself (smoke and N-nitroso compounds), I'd assume a large part of the carcinogenic risk of processed meat can be explained by the presence of these compounds.
The sodium triphosphate that's in your chicken is technically a preservative. However, sodium triphosphate preserves the meat by retaining water, slowing down the drying process.
Sodium triphosphate itself is perfectly safe, I think the limits on the quantity that you can add are present mainly because it can be used to cheaply increase the weight of meat/fish. It's also GRAS (generally recognized as safe) by the FDA.