It is GROWTH, that generates back budding. Growth, good vigor and sunlight getting into the interior of the tree are the key elements to generating back budding. The pruning alone does not do the trick. If you prune too heavily, there will be no back budding, because there will not be sufficient growth to generate back buds.
Technique one, pruning in late summer or autumn, will activate back budding. The buds you cut back to will activate the following spring, but buds further back may also back bud if there was enough growth, enough accumulation of sugars to provide energy for interior buds to activate.
Technique 2, pruning new growth back in late spring, or early summer, this will primarily activate the buds at the base of the new growth pruned. They usually will not grow until the following spring. This means the tree remains a static size without adding a lot of growth all summer, hence not accumulating as significant an amount of sugars. This is important in a "finished tree" where you do not want rapid growth. This is counterproductive in a tree in early development, as it slows development. This will stimulate back budding to some degree, but because it lowers the overall energy, the back budding will not necessarily be profuse.
You mention your tree in the image is recovering from repotting and pruning root system to adapt from a nursery container toward a bonsai container. Your best bet is to let the tree recover without pruning. Once you see vigorous growth, then you can resume pruning.