Hi Nikolay,
About Goenka, hahaha, okay.
It's just I believe that if we don't agree with someone, why we have to waste our time talking about them?
As for your question:
"a simple concentration meditation with focusing on breathing can have an aim of both Vipassana or Shamatha, depending on what we trying to achieve and how stable our mind is."
-First, let me talk a little bit about "Ānāpānasati".
Sati means mindfulness;
anapana means breathing (inhalation and exhalation).
When we start doing Shamatha (meditation) we need something as the base (subject) of our meditation, say, counting beads, chanting etc. Whenever something outside and/or inside (our thought) distract us, we pull our attention back to our object of meditation again and again. Hence we are doing our Shamatha (meditation), to keep our meditative state or one pointedbess of mind. And at some point, if we don't attach too much to that so calm/blissful state of mind (meditative state), we will learn to use that stat of mind to dig deeper inside our mind. And that is Vipassana or insight development.
As for Ānāpānasati is the practice of "sati" (mindfulness), not meditation (Samadhi). Sometimes it's hard to convey its meaning for mutual understanding. For example, I know the word "Samadhi" more than "meditation" as English is not my first language. And that was why I know "sati" (mindfulness) is not meditation (Samadhi). But again, I don't know if meditation has many meanings including sati or not. But for the sake of clarifying, I have to separate them here.
Sati (mindfulness) means attentiveness; detached watching; awareness
While Samadhi (meditation) means concentration; one pointedbess of mind; mental discipline.
So when we start practicing Ānāpānasati", we are practicing sati (mindfulness) by using our breathing as its base (yes, we can use other objects as its base, for example, the movement of our body, walking etc.) If we focus
too much on our breathing, it might turn to be meditation, not mindfulness. It's not bad if we get our meditative state by that.
But it's not the aim of mindfulness. Roughly speaking, if we focusing on breathing (meditation) we cannot interact with our mind. Whenever our thought arise, our awareness always shake them off and come back to our breathing. But as for the awareness of mindfulness, it just lets the thoughts arise, and just watching them (observation) without doing anything, not even trying to stop them. Just watching until they fades away by themselves. That's all. See the difference?
Hope this make to clarify it a bit.