Ethan J. Jackson here, Founder/CEO of Kelda, and author of the post.

Thanks for the comment! You are, of course, right, once the initial OCR standard was developed, it acts as sort of a thin-waist under which tons of innovation in container runtimes are possible.

The main goal of the post was to provide a high-level overview for folks new to containers that need a beginning working model on what this stuff is all about. So I elected to omit this (and other) details in the hopes of being a bit easier to grok. But I think you’re right, I could definitely have clarified the point a bit more.