Follow up from https://github.com/facebook/react/pull/11616.

Here's one I found. These two invariants:

https://github.com/facebook/react/blob/7e7127387ba64f57299eaff8656542cea6fb3a2d/packages/react-reconciler/src/ReactFiberClassComponent.js#L330-L343

are in a function that's behind a DEV block:

https://github.com/facebook/react/blob/7e7127387ba64f57299eaff8656542cea6fb3a2d/packages/react-reconciler/src/ReactFiberClassComponent.js#L447-L449

I don't think this is intentional, but need to verify.

There may be more. I'll use this issue to track while https://github.com/facebook/react/pull/11616 preserves existing behavior.
textNode2 = e.childNodes[2];
          expect(e.id).toBe('parent');
          expectTextNode(textNode1, '  ');
          expect(child.id).toBe('child');
          expect(child.childNodes.length).toBe(0);
          expectTextNode(textNode2, '   ');
        },
      );
      itRenders('a composite with multiple children', async render => {
        const Component = props => props.children;
        const e = await render(
          <Component>{['a', 'b', [undefined], [[false, 'c']]]}</Component>,
        );
        let parent = e.parentNode;
        if (
          render === serverRender ||
          render === clientRenderOnServerString ||
          render === streamRender
        ) {
          
          
          expect(parent.childNodes.length).toBe(5);
          expectTextNode(parent.childNodes[0], 'a');
          expectTextNode(parent.childNodes[2], 'b');
          expectTextNode(parent.childNodes[4], 'c');
        } else {
          expect(parent.childNodes.length).toBe(3);
          expectTextNode(parent.childNodes[0], 'a');
          expectTextNode(parent.childNodes[1], 'b');
          expectTextNode(parent.childNodes[2], 'c');