Does that make it OK? I mean, something as important to the web as getUserMedia is broken on websites only if you pin it to the home screen. Forcing people into Apple's walled garden doesn't seem like an acceptable excuse.
It could also be a security/privacy decision to leave it broken but safe until they can implement camera access through WebViews securely.
The closest to any official reason I could find is a dev letting us know that mum's the word:
>I asked about this internally and the answer is that, right now, WebRTC is only supported in Safari. No WKWebView, not even SFSafariViewController.