A lot of people think that, which is too bad really - since it makes products that contain "real meat as the first ingredient" but no other quality sources of preotein look attractive to people when they are not.
Many of them contain only around 25% meat by fresh weight (with all the water still included), which then shrink to about a third to a quarter of the weight after most of the moisture has been removed.
This means that for example if you have a recipe that includes 25 pounds of fresh meat per 100 pounds of ingredients before processing, the finished product will only contain around 6-8 pounds of meat - since all the cereal grains used are already pretty dry and don't "shrink" much in the drying process.
Meals do differ in quality though, the "chicken meal" that different companies uses isn't necessarily of the same quality. Think for example that it could either be made of spent egg farm hens that are at the end of their life cycle and don't have much meat on their bones, or from the same type of chickens that are sold as broilers or fryers at the grocery store.
I hope that clarifies it a little.