Maybe answer my question:
It seems to me that the answer could be of some importance to bonsai development and would maybe reflect on the video.
And maybe also
@Adair M can explain what 'course' means when describing a needle shoot on p. thunbergii (e.g., long, long necked, thick/fat).
Oso,
It can be a method for reducing internode length. But one I would only use in the early phases of development, not when the tree has reached the Refinement stage.
Partial shoot pruning (aka "candle breaking") is best performed when the candles have stopped lengthening, and are starting to form needles, but the needles have not broken out into the open. At this point, the candle will be thin in the barren "neck" portion between where the candle emerged from the old growth to the area where the first needles are on the candle. The area where the needles will emerge will be thicker. The candle/shoot looks somewhat like a corn dog on a stick.
The candle is somewhat "snappy", in that it's easy to break off a section. Bend it and it breaks like a carrot. You can shorten the candle but make sure you leave some of the fatter portion. That's where the new needles are. Breaking at this stage will allow the shoot to develop a new terminal bud for the following year.
This method shortens the candle and thus the internodes.
However...
The needles will be full size since they still will have all summer to grow long.
Usually, there is one primary candle produced in the spring at each terminal tip. By breaking it short, the branch won't extend as long, but it still lengthens without making any additional branches.
And, the "neck" will still be there. That area between the previous year's needles and the new needles has no buds. If you have a long neck, it makes for long internodes.
When the candle/shoot is completely removed, the new candles that emerge typically have very little if any neck. Usually, more than one candle will grow after a decandling. Two, three or even more new candles will grow where before there was only one. These new candles have virtually no neck, will not grow as long as the primary candle was and will be thinner. The needles will be tightly bunched together. These characteristics are all very desirable. If there are too many new candles produced at a terminal, they should be reduced to two.
The question was asked about what makes "needle buds" coarse. It has been my experience that needle buds grow differently than the "resting terminal" buds. When they grow out, they almost always produce a cotelon between each pair of needles. And the length of stem produced between pairs of needles is longer than the tightly bunched needles produced by the summer terminal candles. After the first year, their new candles become normal.
So, if you're not in the Refinement stage, you can induce needle buds. After a couple years you wouldn't know the difference. But for refined trees they're undesirable.