Handstand pushups have tremendous application towards building upper body vertical pressing capacity. Perform them with less efficiency, however, and the performance transfer will diminish.
Notice in the first part of the video that during the descent of the first couple of reps, my neck is flexed; I’m looking towards the abmat. This is NOT what we want.
The latter reps show better form. Note that the head is neutral during the descent of each rep; my eyes are looking across the room as I go down and press up. The finish of each rep ends with the head being pushed through the arms.
This application of this pattern to other overhead barbell movements is revealed in the second half of the video.
The first few reps of the barbell presses are NOT what we want; the bar is pressed away from our center of mass. At the start of every rep, we want the head to remain neutral and then complete the movement by pressing the head through the arms; the weight is firmly over my center of mass.
Quality execution in one movement may be more difficult at first, but is ultimately healthier and has more profound transfer to other movements.
Do yourself a favor and check your ego when necessary, practice excellence now, and work towards long term mastery.