Well whether you do a static Yoga pose or a vinyasa yoga exercise, you have to pay attention to details within the body. This includes attention to muscles, bones, breath, and also starting at a point (drushti). All these require a lot of effort on the part of the mind and brain. Since it is quite challenging, several persons consider this as a Meditation of some kind. Because, this makes the focussed and sometimes even calm as the chatter reduces a lot.
However, the focussing described above is not a Meditation process. In Meditation process one needs to focus only the mind at a given space or object without having to do anything with the voluntary bodily functions. This way the entire mind can be focussed in the Meditation itself.
Only the later kind of Meditation leads to the classical Samadhi or Super Conscious state. However, the earlier process is what most people want and is beneficial to them in that respect. Both these statements can be verified easily from the available data.