> Does this follow the relevant standards, which I presume exist? Yes. For <video> and <audio>, the spec only says the UA "may" (RFC 2119) follow the autoplay

> Does this follow the relevant standards, which I presume exist? Yes. For <video> and <audio>, the spec only says the UA "may" (RFC 2119) follow the autoplay steps, and the play() method only does anything "if the user agent and the system allow media playback in the current context". For WebAudio, the spec says, "An AudioContext is said to be allowed to start if the user agent and the system allow audio output in the current context". So the UA is always allowed to decide whether or not to start playing media.