Did you think there was a requirement to have code?

For normal blog posts, no, but OP is submitting as "Show HN" which requires it to be something readers can try on their own:

>Show HN is for something you've made that other people can play with. HN users can try it out, give you feedback, and ask questions in the thread.

https://news.ycombinator.com/showhn.html

This is an on-topic blog post, but it doesn't seem to fit the criteria of a Show HN.

Hm, how can you tell it was a Show HN? Doesn't seem to be in the title. Maybe it was before?

Yeah, the title originally had the "Show HN" prefix. Looks like it's been updated since.