@Yvonne G - not sure what he was going after, but he would have kept going if I didn't stop him - he made it a bit higher to where the trunk straightened all the way, and looked like he was committed to continuing up.
@Jacqui - he's done this 3 times, he gets about 6-8 inches higher, and then I pull him off. I feel like he could go higher, but would rather not have him fall backwards, so have never let him. I have a stump in my backyard as well, and he has never had any interest in that, only the full tree.