That extra 10% is essentially a salt water solution. It's also called Pure Profit for the retailer. IMO, injected/tumbled meat is a sleazy way of shafting the indifferent customer by getting him to pay more for less under the guise of delivering a moist and tender meal. Ribs and most other meats have a high enough moisture content really don't need any additional help to make a moist final product when cooking appropriately for that cut.
The saline solution does to an extent serve as a brine. However, with that Super Wally meat, you don't have any control over what went into that solution. Should you try to brine a pre-injected chicken, for example, virtually none of your seasonings will be absorbed into the meat because the cells are already saturated.
I think you're right to be wary and suggest you look elsewhere for a reputable butcher who sells only real meat. That gives you the option of tinkering with solutions at home, if you wish. Chances are that he needs your business more and would be responsive to your needs than your local ConHugeCorp Mega Mart.
This hot button topic came up about 18 months when Wally and many other big grocers began forcing more injected/tumbled meats into their display cases and they were mostly unresponsive to the small number of complaints made to them. Buying that doctored meat now at any price would only further prove to them the consumer doesn't care. Here's your chance to prove them wrong.
/soapbox mode off
Ken