deepObserve callback getting called multiple times within a single runInAction function

I have a simple case that looks something like this:

const myArray = observable([]);
deepObserve(myArray, () => {
   console.log("array update");
});

runInAction(() => {
   myArray.length = 1;
   myArray.length = 2;
});

The log in this case runs twice, once for each length modification, immediately after each.
Is this normal? I would expect that because those length updates are in a runInAction, the observer only gets updated once, after the action is fully executed.

Start by tracing deepObserve callback scheduling around the observable array and runInAction example, then reproduce the two length updates locally. Compare the callback count with the action boundary and document the expected behavior in a focused regression test; done means the observed behavior matches the intended batching semantics.