Hi @prok_in,
Great question!
It's not completely static. New logs appear, old logs get disqualified, sometimes log operators ask us to stop submitting for a little while and then we may resume again.
I believe presently we submit to Icarus, Venafi's gen2 log, Sabre, Mammoth, and one of Cloudflare's new logs. The staging environment only submits to test-tube.
The three certificates you shared were issued in three different points in time and the # of logs we were submitting to can change as I explained above. It isn't a constant.
Hope that helps explain!