I'd go back and let him know that it's illegal to adulterate ground product or sell it as 100% ground beef when anything at all has been added. The state inspectors can seize samples on any visit for analysis and can shut down the store if intentional adulteration is found.
This is entirely correct. The inner ground meat had just not been exposed to oxygen yet and was still in it's native blood color. The oygenation of meat film is standard procedure and approved, but it will allow oxyen to pass so it should not be used for long term storage; repackage into sealable bags or containers.
Eventually the ground meat will turn bright red completely through if it has not been ground too tightly, as oxygen can seep between the strands of ground meat to oxygenate it. This is why it is 'squiggled' into a package, to allow the oxygen transfer into the package to 'bloom' the meat; eye appeal is buy appeal.
Now if they're selling soy protein additive ground meat then yes, water and soy protein is added in copious amounts, extending the profitability of the grinds, but also giving a more healthful product too. But, this has to be indicated in large letters on the packaging.
The third possibility is that they are 'constructing' their grinds; in other words using fatty trim and lean, local bull beef or imported bull beef. Usually from New Zealand or Australia (grass fed). Very lean and tough, but great to add to grinds as it is 90-95% lean. If imported it comes in 60lb. frozen blocks of frozen solid bull beef. You cut it up on the meat saw into slabs, then into sticks to defrost a little before grinding; sometimes very little. Being frozen, it is retaining some moisture and when thawed iwll leak more prominently.