Please clarify how to use canary ISO

In the page I see a daily/canary and a daily/live. Until now i installed using the daily/live but I’m curious about the purpose of the canary ISO.
Some time ago I successfully installed once from canary ISO and i found the snap: ubuntu-desktop-installer is present also if not listed in .manifest file.
Also the testcases for the canary image are missing in

I received an explanation: Foundations Team Updates - Thursday 24 Aug 2023