The issue boils down to this line:

First off the bat, I realize this may be impossible to change due to backwards comp. Still, let's discuss.

Task A awaits task B. Someone cancels task A. Task B gets cancelled instead.

This probably makes sense in some contexts, for example if task A is the logical owner/parent of task B.
But in my case, task B was created in a long-lived taskgroup. Its lifecycle is independent of task A. They are now coupled by this invisible link created by the await.

I wonder if we could make this cancellation forwarding be skipped in some cases, like if the awaitee was created through a task group (since that mitigates the danger of leaking tasks).