K.G.
This is super normal. My son's preschool started at age 2, and so I saw many boys and girls go through potty training. Many, many of the boys and girls wouldn't do #2 in the potty (including my son). They feel like they are losing a limb or something in the potty. It really scares them. W/ my son, we did not get upset w/ him (you want to avoid a power struggle at all costs). He usually would hold his poop until we put an overnight diaper on him and then he would poop (he had actually been dry at night for some time before he was daytime trained, oddly). We helped him take the diaper into the bathroom and had him roll the poop off the diaper and into the toilet and flush. Two things helped were the book "Once Upon a Potty," and a sticker chart. For the sticker chart, we had a kind of sticker he really liked that he could only get if he did #2. None of this worked immediately. It took about two months after he was pee trained for him to consistently use the toilet for poop. I think the most important things to remember are that he is probably scared to have his #2 drop from on high, you want to avoid a power struggle at all costs, and this is a very typical pattern. Also, is he using a potty or a toilet? If he is using a toilet, give him a step stool so that his legs aren't dangling. It's almost impossible to poop w/ your legs dangling. Do give him things like prune juice that will encourage him to go more often if you can.