The iCloud settings are slow, because the backend is slow, not because it is a WebView.

On your phone, open Settings, then tap on your name (apple id), then tap on "payment and shipping", "subscriptions", or "media and purchases" -> "view account". All of those are webviews.

What's your point? You're just repeating what they said. WebViews which reach out to slow backends will render slowly. That's about it.

I didn't say anything about slow, even though they are indeed slow. All the elements (spacing, sizes, etc) are clearly off.

If you're using that as indication for WebViews than you'll be miss-identifying a lot of native apps as well, because that's all set by the developer - both with native apps and with WebViews.

That is just one of the many heuristics that I use.