There was a time when I was able to get into sirsasana with straight legs. The fear to fall returned and from one day to the other I was no more able to come up with straight legs.
The trick: I walk with my feet as close as possible. Finally the legs lift from alone. I must have forgotten this.
Yoga is controlling I wrote a few days ago. This also means that we move into an asana controlled. I should be able to stop my movements any time I want, no matter if I get into the pose or out of it. What is true for sirsasana is also true for salamba sarvangasana (and for other asanas, too). It's not letting go and falling out of a pose. It's a controlled movement.
The breath initiates the movement. Re sirsasana I inhale, inhaling matches with the movement.
Picture 3: Oh, the legs are parallel, as it is supposed to be when doing sirsasana in the closing sequence.