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.
var propValue = props[propKey];
    if (propValue == null) {
      continue;
    }
    if (propKey === STYLE) {
      propValue = createMarkupForStyles(propValue);
    }
    var markup = null;
    if (isCustomComponent(tagLowercase, props)) {
      if (!RESERVED_PROPS.hasOwnProperty(propKey)) {
        markup = createMarkupForCustomAttribute(propKey, propValue);
      }
    } else {
      markup = createMarkupForProperty(propKey, propValue);
    }
    if (markup) {
      ret += ' ' + markup;
    }
  }
  
  
  if (makeStaticMarkup) {
    return ret;
  }
  if (isRootElement) {
    ret += ' ' + createMarkupForRoot();
  }
  return ret;
}
function validateRenderResult(child, type) {