Yeah I dont know why some of them are insane. They're not all like that. It just seems like in every class of trees (I graft 100 annually) there are always some that are crazy vigorous, and others that are not. The crazy ones stick out, the ones that are not are lost in the sea of giants.
My hunch is it may have to do with the quality or lack of quality of the actual graft. I also notice that those few tbuds are just beautiful. There is a noticeable difference when you have a tbud just breaking dormacy late march that is already healed vs a fresh whip & tongue or cleft graft. The buds are a lot more vigorous probably because they have a nice established root system feeding the tree.
But for me it's a balance. Every fall I go through all of my trees and identify which ones will go to the farm in spring for planting and which ones will stay another year or more of nursing. This method basically keeps me setup to have a steady flow of 30-50 trees for planting every spring, which is just about the right number for us. It's manageable.
One other thing I did this year, back in june. I basically cleft grafted a bunch of trees that failed to graft last year. They grew into 4-6' whips, B118 rootstocks. Early june I had a bunch of scion left over, I just went out there and cut them all off at like 2' off the ground and cleft'd them. That actually worked out really well, some of those things have already grown 12" or more. I think it's important to try and utilize your failures, either through t-budding or clefting like I did. I think i like this cleft grafting on the failures better than the t-budding. The tbudding is a hassle getting down on the ground.
I have 4 trees on G30/B9 in my backyard at home. 1 zestar!, 1 sweet 16, 1 honeycrisp and one Cortland. This spring i also turned a few of them into frankentrees. I have limited space, can't plant more trees, so what do I do to add more varieties. Add a branch of this, add a branch of that. It's fun and I basically had 100% success. I easily added Liberty, Florina Q, Wolf River, Northern Spy, and Kerr to 3 trees. I'll probably add a few more varieties next year. here's a picture of one of the grafts which I pulled the tape off today. I think this was done mid to late may, looks great and already grew about 14".