You've nailed one of the trickiest parts of parenting: telling the difference between a kid who's overwhelmed and one who's learned that shutting down gets a reliable reaction. Both are real, and the ...
That distinction you named is the heart of it. The same still surface can mean an overwhelmed nervous system needing co-regulation and space, or a learned pattern where pausing brings a predictable response. Wondering gently what came before it and what restores connection afterward often clarifies which story fits this moment.
1