My original thought was that it had to do with a DB query plan. ie: converting a SQL statement to a set of operations.

Reading through this, I came to the same conclusion. I am really confused as to what a plan is in this context.

My best guess is that it is similar to the DB query plans above. It sounds like given a set of composable higher-order functions and a problem, students can use those functions to solve the problem.

Maybe I’m wrong?

The "plan" they are referring to is an abstract one, about how to transform input/output on some data

Example: you make a REST API request, get back some data, and need to transform it and save it as CSV. What are the steps you take/functions you combine to do this?

I also thought this was about DB query planning.

Is this usage of the word a known technical term, or is it just something they made up without explanation?

I've never heard of it as a technical term but I'm not familiar with pedagogy, so my experience might not be worth much here lol.

I assumed it was planning what students are going to build before they code it up.