Blink have the answers, for sure, because they spent a whole heap of research time on getting battery use down to the bare minimum, and have continued to lower the demand with the XT2. Blink shared a number of useful pieces of information with me when I contacted support. It was quite a struggle, with a bunch of failed answers, until I finally got hold of a design engineer, who emailed me several key points with regard to power consumption. Sadly, I wasn’t asking the questions you were, so there is no answer in my learned knowledge that can help you. That having been said, my success in tracking down the info I was after, might point to them being prepared to share it with you, if you get hold of the right person.
Not that this is information I gleaned from my contact with Blink, but I’m fairly sure you can take a whole heap of snapshots for a short section of video, in terms of energy consumed. I get what you say about it not being a 25th of a second, times length of 5s minimum clip, i.e. 125th, but still, I think it will be insignificant, in comparison.
Doubt you will hear in here from anyone from Blink prepared to share that info and I doubt anyone in the community has done the required tests. I hope they have, and will keep an eye on your thread to find out.