I am pretty sure that the test was badly done and the whole 50% thing was the result of shitty sampling. Yes, they have soy protein additives but fake chicken is more expensive than real chicken and the tests were never confirmed by a second lab.

A lot of fast food does end up having meat that is significantly lower than 100% meat just by doing seasoning and preservatives. Taco Bell for example has a crazy amount spices and filler ratio which is partially due to the fact that meat volume is reduced as the moisture is cooked out. They are still excessive though.

Subway gets picked on the most both due to how it has the most locations (or did at one point) and it brags about the food quality. Nobody picks on KFC for how fatty their fried chicken is because we know it is fatty. Subway played themselves.