Rio Burton, creator/publisher of the crowdsourced Branches Entwined and Broken, was kind enough to reply to my comments on the book. Here is the reply, reprinted with permission:

Hi Tom!
Thank you so much for your support, especially it being something out of your comfort zone. It was completely new for me too haha! I took a step back from colour to work on values and textures. I chose the manga size because honestly, I love that size more! (It’s going to be much easier to travel with to conventions being smaller haha). You all gave me some wonderful experience printing the book and seeing it in a physical form. Going forward I will strive to keep improving on my stories and art! It’s certainly a different beast between manga and US standard-sized comics.
Thank you again!
Rio
So there you go. A little extra insight on the format and what Rio thinks about it. Pretty cool.
I’m actually looking at that manga format myself for when I reprint a collection of the Hologram “Counting the Days” arc. I’d think that it would be conducive to a slightly larger, but not distorted, version of the quarter-page minicomic size. Branches Entwined and Broken certainly gives me additional inspiration to try it!