I've heard conflicting advice on cut paste. Some say it isn't needed and others say you must do it? Is there a source of truth on this subject?
It is always anecdotal evidence from bonsai hobbyists based on what Japanese grandmasters do, vs modern horticulture insights that discarded the idea of using cut paste based on scientific insights in plant physiology. In the end the pro-cut paste argument comes down on that bonsai are different from all other plants. So we falsely used cut paste on all plants, but just for bonsai, by accident, it turned out to be the correct treatment, even though the ideas behind using cut paste were wrong. And the reasons for doing is personal observations. People didn't use it at first, and had a few plants die. Then they became more serious growers and became more skilled, and also started using cut paste, and less trees died. So they conclude the cut paste must be the reason.
People that agree on usage of cut paste disagree on what cut paste to use and what it protects the plant against. Even if they are correct, they don't have a strong argument. It is basically 'better be safe than sorry', but that ignores the harm cut paste may do.
The main issue with your tree is that you left no leaves at all. Apparently in Japan they can often get away with this because of their hot humid summers. If you have weather were growth is less vigorous, or dry weather Californian/Mediterranean weather, this is not safe to do. Not sure if this is completely correct, but it makes some sense. If the tree grows too slow to put out new growth, with new leaves maintaining a water column inside the plant, before the tissue dries out, I can see how it can die.
