In our practices, we seek to awaken the consciousness and free it from conditioning so that it can see without filters of any kind. This is what samadhi is: the ability to perceive objectively.
These are the filters we need to extract consciousness from:
physical body (physical sensations, state of the body)
vital body (energetic sensations)
astral body (emotions)
mental body (thoughts)
causal body (willpower)
Each of them is filled with attractions — sensations — that hypnotize the consciousness.
Those who remain entranced by physical sensations maintain the consciousness as conditioned by physical manifestations. As such they remain unaware of the more subtle sensations in the vital, astral, mental, and causal levels.
Those who manage to free the consciousness being fascinated with physical sensations must then free it from the vital, astral, mental, causal. Each is more subtle than the previous.
All of this is what is discussed by the Buddha as "skandhas," and in vedanta as "koshas."
Therefore, knowing this science, it is enough to charge the consciousness with energy (via pranayama, transmutation, etc) and it can escape all these sheaths immediately, instantaneously, thus rendering useless all those breathing exercises. That is why you do not find the discussed here.
Stated by manner of analogy, one does not need to know how to put air in a bicycle tire if one is flying with wings.
Many people persist in those exercises, and that is fine, there is nothing wrong with them. The danger however is people remain focused on the breathing, the abdomen, the lungs, etc - i.e. physical matter — and never abandon it. That is why they never access the awakening of consciousness.
So, we simply prefer to get directly to the point.
"Do not worry; cultivate the habit of being happy." - Samael Aun Weor