Drew,
I’m not sure I understand why it matters to much because if you cut the bottom at a 45 or top either way your roots come from the nodes you have below the soil line and leaves come from those above the soil line. So the deeper the pot the more nodes and the greater your odds for one node rooting. The angle of cuts at the nurseries when I’ve watched them I understood to always just be a way of marking bottom from top. The 45 went on the bottom only to mark it as bottom. When I receive scions they are frequently the same way I suppose because that is the way we graft. Perhaps it’s not the best way and something many of us do because it’s what we do when we graft. If you watch the video you will note he cuts his just the same as I do mine and as I’ve seen many do theirs. Explain a little more about your process if you would. I always figure I try and get at least 2 or more nodes below the soil line and 2 or more above and that’s reasonably good form but 3 is better. With pruning I tip my branches just past the buds straight across. Now I don’t do that type of pruning much but apples need invigorated at times. I find myself doing it frequently ( every other year) with honeycrisp. You can see my tipping pruning method here Tipping to make a bushy more productive fruit tree