Interesting reaction, thanks for sharing!
Traditionally, there are claims that the energy from unresolved emotions or other mental trauma can be "stuffed away" in different parts of our bodies. This is similar to how the body may store certain toxins in our fat cells when there is too much for it to detox in the liver, etc.... This "stuffing away" causes tightness and energy blockages. Because this energy is being held in the physical body, rather than the conscious mind, people are often unaware of even carrying around such mental/emotional baggage and just chalk it up to some physical deficiency. It sounds as though you have been experiencing releasing that stuck energy and freeing up the blockages for energy to flow again.
If that sounds too "esoteric", simply consider that you are relaxing some areas where you had previously been "holding tension." Certainly a very worthwhile benefit, but I would agree, not "brain mastery!"
Indeed as you suggest, it is likely this "held tension" was a gating issue for you to continue on to work on other issues. There are not a lot of reports of people going through a second round of BrainEv, but from the few that are on here, it seems those have experienced increased and different benefits. Interestingly, for some people, the experiences of the second time through are sometimes drastically different than the first time (ie. levels that were "easy" before become "difficult" and vice versa....)