Apple approving the update to Revisions is the big reason. I wasn't sure if that was going to happen. For years that app was listed on my App Store Connect developer page with the warning icon attached to it.
...and yeah, I'm tired of having the same debate. A lot of people say they want a digital version. Look at all the likes! 
(Thanks to everyone that liked the second post in this thread. That's very encouraging!)
It certainly wasn't an impossibility...
That was last November.
You asking for a digital version might have been the turning point. Not long after our conversation is when I tried relaunching Revisions. It worked! After that, I started working on this project. That was April. I'll be working on this project through May. While there's still a lot of work to do, being able to use the "Photics Book Engine" does make the job a lot easier.
Today I've been mainly working on improvements to the way the "Photics Book Engine" works. I think it's nice! 