Google recently indicated why they do not disclose most algorithm updates.
The reason being that Google does hundred of changes per year.
“We tend not to disclose most of the updates.
We make them like hundreds a year, so for the most part, it doesn’t make sense to say oh, we made a change today, we made a change yesterday, we a change today, we made two changes yesterday.”
You can view the video here: https://www.youtube.com/watch?time_continue=480&v=L_HB7i5A-QY