This is "Runestone Components" Javascript, which we are using for a (new) class
of interactive exercises.
When hosting on Runestone, the HTML ID is used in the "assignment builder" to
help instructors know which exercise they are assigning. This is part of
Runestone's HTML-only history.
We put exercise *numbers* and titles (if authored!) into a "manifest" as part of
a PreTeXt build meant for hosting on Runestone. So it is a Runestone
enhancement to use that information in the assignment builder.
"But I'm not hosting on Runestone (yet!) and I don't want to see those IDs!", I
hear you say. We hear you.
Another step on the road to greater interactivity and fantastic hosting at
Runestone, while preserving independent hostability.
You could check for a Runestone Components issue on GitHub, and if you don't
find one, then making an issue would give us a place to track this. Feel free
to cut/paste above explanation into that.
Rob