Hi there - I found this article really interesting, as not from the Zen tradition myself. For this:
"Sekida's explanation of why this happens (a build up of spiritual energy) is obviously not a very useful model and at best a helpful metaphor for what it feels like to undergo kensho." 

I also find this way off. If you want to use metaphors then it's more about what is let go of, allowing a direct realisation, rather than a building up of something. At least that's my personal experience and those I know.

Just to say that Culadasa's approach is as much Mahayana as it is Theravada in background. He draws on both.

take care

including but not limited to books like The Mind Illuminated, Mastering the Core Teachings of the Buddha, and The Seeing That Frees

What a trio of books! All three of those sit prominently on my bookshelf, and have had significant impacts for me at different times. I absolutely treasure The Seeing that Frees. I am so happy that Rob lived long enough to give birth to that book, and his many talks online - though of course would have loved to have seen his later teachings on Soulmaking in book form.