I found some hints - straight from the source, Google's design team - to the reasoning behind the "G" design, and why the alignment of colored arcs turned out that way.

A short video that demonstrates the intention of the lines: https://g-design.storage.googleapis.com/production/v6/assets...

It came from this article, Evolving the Google Identity (https://design.google/library/evolving-google-identity/) under section "Google G Construction".