Ok I posted your pic on a FB site where many of the members are in the meat industry and got a few good responses as to what happened here.
*PSE pork loin injected to compensate so that it would be moist because PSE pork does not hold water and cooks to a dry texture even when cooked to perfect temp. This was over injected. Most likely bought at a big box supermarket or wholesale club
* If it is injected it could be bacteria creating gasses inside the product. So it could be lack of cleaning injection needles or not disinfecting them.
*Over injected with a brine containing phosphate
Without phosphate no holes would form
*as someone who works in the meat processing industry , direct competitors with Tyson actually, E.W. above is 100 percent correct
That is over pumped with phosphates...
and to be even more specific it's probably not pumped , it's tumbled most likely.
*There are two things that could be causing this one more likely than the other. The most likely reason is that it is enhanced and the producer didn't have their pressure dialed in correctly on their injection needles or there was air in the line. Either way, in this scenario, the solution was pumped with air also entering the muscle.
Alternatively, and probably less likely, this is, in fact, voids left by some variety of bacteria that made their way in during the pump.
Either way its from the pumping procedures and not necessarily the ingredients.
Hope this helps answer the mystery.
Should have just listened to Chef JJ