That pretty much goes against everything they say in the book I have. Of course it was published in the 70's...
PRUNING YOUR PLANTS
You can increase foliage production if you prune your plants.
Clipping will encourage secondary growth and allow light to reach
the less mature leaves.
You should prune your plants for the first time when they are
three weeks old. Cut the top of the plant, severing the stalk just
above one of the leaf clusters.
These clippings can be dried and smoked as the first rewards of
your labors. Don't expect more than a little buzz however. The
plants are still young and have not had time to reach a mature state
of high potency.
When you prune off the tops of your plants the secondary
growth above each leaf. They will be stimulated and will grow into almost
like branches themselves. Many leaf clusters will grow out of
these branches and more branches will grow above each leaf.
By pruning your plants you can get them to grow bushy rather
tall and spindly. When the secondary branches get at least four
sets of leaves, it is time to prune them just as you did the main stalk
the first time you trimmed. Out of each of the four leaves you left on
the secondary branch, four new secondary branches will be
stimulated to grow and so on. Clip the new secondary branches about every ten days.
You may also trim off main leaf clusters to promote secondary
growth. Taking off some of the big leaves will allow more light to
reach the branches underneath them. The top leaves of each branch
are the best and so by stimulating more branches to grow, you will
have more top leaves.
As the plants grow you can continue pruning them in this
fashion. The clippings will provide you with a constant stash and at
the same time, your plant will be producing more and more leaves.
The quality of the plant also increases as the plant gets older. You'll
just get more and more and it will get better and better.