If Apple uses this CSS liquid glass effect in their apps, it'll pass App Store review just fine.
Do you see the issue now?
Do you have any evidence of this claim? It's possible that neither Apple or third party developers are able to ship apps through the app store with it.
But when Apple creates self-serving APIs in a web browser engine, it's just another private entitlement, a red herring and their right as the proprietor of Safari.
The lady doth protest too much, methinks.
It appears that this particular API is restricted to embedded webviews, too (doesn’t work in Safari), so it has no bearing on the open web, unlike APIs such as WebUSB in Chrome.
Citation needed.
The blog article speculates this, but there is no proof.
> Apple App Review Guidelines: 2.5.1 Apps may only use public APIs and must run on the currently shipping OS.
https://developer.apple.com/app-store/review/guidelines/
And here's the (private) field that needs to be enabled on your webview to enable the CSS property. Otherwise (according to the author) it's just ignored: https://github.com/WebKit/WebKit/blob/613c42873c56e2b2073f91...
They do not publish any "proof" to cite beyond what they write there. And they interpret and enforce the rules at their own whim.
The private API is here: https://github.com/WebKit/WebKit/blob/613c42873c56e2b2073f91... it's on WKWebView and resembles other private APIs they forbid access to
Apple absolutely does reject apps for using private APIs. Here is a famous case where they started rejecting Electron apps for private API use: https://9to5mac.com/2019/11/04/electron-app-rejections/ You are welcome to sit and wait for Apple to publish proof that this new private API is just like the others but you shouldn't bother others demanding they cite it for you when clarification will not come for this particular API and there is already precedence on how they handle it categorically. You also shouldn't spread false confidence that it's OK to use these APIs due to lack of "proof" which meets your own standards when it can and has resulted not only in apps being removed but also threat of developer accounts being terminated. (Even if this is rare.)
I understand it can be confusing: they don't do it consistently and they change their enforcement of it over time as they please. Even when it's not done automatically, they can and have inspected closely "by hand" if they are looking for a reason to punish. It is a liability.
