In case you didn't know, the photo in this article shows two 8-week old Japanese Black Pine seedlings soaking in rooting hormone after having their tender young root cut off completely with a grafting knife. If you're thinking, "that sounds like a good way to kill some pine seedlings", you'd be at least half wrong.
This "Seedling Cutting" technique is now a standard among avid American bonsai enthusiasts, and is fabled to reduce the height of the finished tree and increase the swelling at the base from a very young age. A swollen base is a good thing because you want a fat trunk in "serious" pine bonsai and short compact branches. It might seem a bit odd if you are into horticulture to both sabotage the seedlings natural habit and then dunk them in a rooting hormone, but the technique has proven to be quite popular and can be quite effective.
It's human nature to experiment, document, and find new and various ways to reach a goal. With bonsai hobbyists you will find an avid group of people who like to tinker with their plants; to make a slow process faster; and to seek methods for improvement. Bonsai can take many years to grow and develop, but it's the fun had along the journey that bonsai hobbyists find so interesting and fulfilling. If your interest in bonsai expands from being a general plant enthusiast or "bonsai parent" to becoming a bonsai hobbyist with dozens [or hundreds!] of bonsai, you will likely find yourself wanting to work with them endlessly to create results that are both different and unique. My advice to you is to make sure you have more than just a couple plants. Bonsai can be really fast growing given the right conditions, but if you are still learning how to care for plants then take your time, keep reading and learning, and remember to have fun along the way!