I thought the App Store review guidelines explicitly prohibit hidden features and using public APIs outside their intended purpose. Is audio-based fingerprinting just not something review can realistically catch?
The title of the article literally mentions "WebAudio", and the first paragraph states that the author is using a PC. The second paragraph mentions Chrome and Firefox.
Apple and the App Store have zero involvement here.
This is nonsense. Safari also supports Web Audio. Safari does not, however, support Microsoft Windows, which is why the article author didn't mention it.
Moreover, all web browsers on iOS have to use Apple WebKit, so Web Audio support is not actually the fault of the non-Apple browser vendors.
I'd argue it's "silent" though: aliexpress wakes up my audio card if nothing plays, which results in a very faint "pop" sound every time I open the tab.
It's been this way for ~3+ years at least.