The difference from MC-2912 is , as I said, that the blocks do not swap completely. In MC2912 if you do what I described above the block is simply replaced and you have the same thing twice. Here you only have the same block twice until you open your inventory again. I guess that could just be added to MC-2912 but I doubt I am able to do that and even if so, I have no idea how to do so.
I made some changes, I hope you approve 😃