[From the Profiler docs](https://reactjs.org/docs/profiler.html#onrender-callback):

> The Profiler requires an onRender function as a prop. React calls this function any time a component within the profiled tree “commits” an update.

However, given:

```jsx
import React from 'react'
import ReactDOM from 'react-dom'

function Counter() {
  const [count, setCount] = React.useState(0)
  const increment = () => setCount(c => c + 1)
  return <button onClick={increment}>{count}</button>
}

function App() {
  return (
    <div>
      <React.Profiler
        id="counter"
        onRender={() => console.log('called')}
      >
        <div>
          Profiled counter
          <Counter />
        </div>
      </React.Profiler>
      <div>
        Unprofiled counter
        <Counter />
      </div>
    </div>
  )
}

ReactDOM.render(<App />, document.getElementById('root'))
```

I'm getting a log when I click on the unprofiled counter.

Reproduction: https://codesandbox.io/s/react-codesandbox-tnff6

Am I misunderstanding this API, or is this a bug?
const fallbackChildFragment = createFiberFromFragment(
              nextFallbackChildren,
              mode,
              renderExpirationTime,
              null,
            );
            fallbackChildFragment.return = workInProgress;
            primaryChildFragment.sibling = fallbackChildFragment;
            fallbackChildFragment.effectTag |= Placement;
            primaryChildFragment.childExpirationTime = NoWork;
            workInProgress.memoizedState = SUSPENDED_MARKER;
            workInProgress.child = primaryChildFragment;
             
             
            return fallbackChildFragment;
          }
        }
      }
       
       
      const currentPrimaryChildFragment: Fiber = (current.child: any);
      const currentFallbackChildFragment: Fiber = (currentPrimaryChildFragment.sibling: any);
      if (nextDidTimeout) {
         
         
        const nextFallbackChildren = nextProps.fallback;
        const primaryChildFragment = createWorkInProgress(
          currentPrimaryChildFragment,
          currentPrimaryChildFragment.pendingProps,
          NoWork,