I don't know if this makes sense, but he might be doing it in order to "understand" his food. Meaning his brain needs the tactile signals from touching and shredding the food in order to allow him to move forward to chewing and swallowing. My nearly 11 year old still has to touch his food frequently. He says it feels better, and sometimes he says the taste of the utensils, or the feel of them in his mouth interferes with the taste.

I recomend small steps. Pick one meal a week, the least stressful one. Give him a choice of several foods that he is very familiar with, telling him that every bite taken without shredding gets a reward. Like a minute on his favorite electronic device, or an extra minute to stay up, or toward a favorite activity. Then praise, praise, praise each attempt and success, but DO NOT use the rewards in a negative way, like taking them away. Keep them positive always.

When he can get through one item at one meal, then add another meal on another day, with either the same item or another of his choosing. Gradually work your way up to everyday, then change up to two items per meal, once a week, working your way up again.

Also, you can try to give him a sensory prep before hand. have him work with clay or putty shortly before the meal to hive his hands some input. And have him chew gum, or a chew stick, or a couple of carrot sticks, or suck up his appetizer (soup or applesauce, or even milky mashed potatoes) through a straw to prep his mouth.

Allowing him a fidget during meals might help keep at least one hand busy as well.

Try to relax about it though, cuz if you're stressed, then he probably is too. It might be a long road, but he and you can both get there! ;)

My son does this. For him its sensory. Its so messy and it takes forever for me to clean up but its just how he works.

He doesn't quit shred it, but it's pretty close. He tries to pick apart everything, but then he'll shove and shove until his whole mouth is full. It's been a trial, and I choose my days, but he does eat with a fork or spoon, some items. Others I just have to deal with him finger eating.

My son shredds his food as a result of years of people trying to hide his meds in it. Very smart this one!