It is not really advised to bury mj stems just as it isnt many other species in a similar group type and cat, thats just simple horticulture any fool can google.
The fact that you can bury just about any stem from a plant and induce a root is what your seeing but its not something mj prefers and hence my statement that disagrees with that of mj seemingly loving its stem buried.
The fact you still get stretched spindly stems and have to keep pots lower in soil levels so you can bury them would suggest you need to listen to everyones advice on distance to light and how not to stretch everything rather than trolling your irrelevant stretched seedlings in our faces.
Was it your intention to come across like a newbie and fool? Sure doing a good job so far