Comment on Super Crispy-Skinned Slow-Roasted Pork Shoulder by Ray.
Your friend may have cooked the pork partly frozen inside.
Also it is important you use a grilling thermometer not length of time.
Often there is a stall in cooking around 150-160 degrees and will need to be wrapped in foil to get over the stall.
Remove roast when it hits 190-195 and rest insulated with towels or in a cooler for 20-30 minutes and should reach 200-210 degrees.