There are no preservatives used on fresh chicken or frozen chicken, and no chicken has excess fat. There are companies in the marketplace that make these misleading claims which infer that those not making the claims contain these undesirable qualities. There may be many. There is a big difference among the many breeds of chickens offered in the marketplace. Numerous companies compete in order to produce the fastest growing, best feed converting, lowest fat, biggest breasted, disease resistant, egg producing strain.
Geneticists crossbreed continually in order to produce the perfect chicken.
The winner reaps huge rewards, and the latest test flock results are guarded as if they were classified as a national security top-priority matter. However, the best feed converter is not necessarily the best chicken from the consumer's point of view. Most consumers want big-breasted birds. They don't want to see bruises or imperfections. Most have a color preference but don't know why.