11.1 ISO-IMAGES for alpha, beta and RC builds

[Ernie Luzar]

https://www.freebsd.org/releases/11.1R/schedule.html

Shows no alpha builds. Is it normal to start the release build process 
with beta builds skipping the alpha builds?

I see ISO-IMAGES for 11.1 beta1. I don't remembering seeing ISO-IMAGES 
for previous alpha, beta and RC build releases. Is this a new change to 
existing procedures?  Are we going to see ISO-IMAGES for alpha, beta and 
RC builds from now on?

Where does snapshot prerelease fit into the alpha, beta and RC build 
process?

Is this documented someplace?