It does seem like a serious tripping point.
I took a quick look at "containedctx" and it seems like for this case, it would almost be backwards: it would flag the (not-memory-leaking) struct-stored "status.ctx", but wouldn't flag when there is a stored "status.cancelFn" only (which resulted in the memory leak).
Could Go implement a runtime leaked-context detector, like the data race detector? https://go.dev/doc/articles/race_detector