[3.12] gh-114104: clarify asynchronous comprehension docs to match runtime behavior (GH-121175) (#121235)

gh-114104: clarify asynchronous comprehension docs to match runtime behavior (GH-121175)
(cherry picked from commit 91313afdb392d0d6105e9aaa57b5a50112b613e7)

Co-authored-by: Danny Yang <yangdanny97@users.noreply.github.com>