Interesting read, thank you. It brings to mind two pieces conflicting (or complementary) writing advice.
One was from an old writing teacher who recommended drilling down into a subject (like your students’ objects of passion) in order to access some deeper meaning or insight:
The world provides. Don’t look away.
The other idea was from Richard Hugo’s essay Writing off the subject:
There are a few people who become more interesting the longer they stay on a single subject. But most people are like me, I find. The longer they talk about one subject, the duller they get.
I wonder how often your students launch off of their original subject (what Hugo called the poem’s ‘trigger’) and into a new territory that creates a surprising connection; e.g., from honey badgers to humans.