Yea, it is such weird behavior. I can count the number of times I've ever wanted to adjust the volume of the ringer, rather than just turn it on/off, on one hand.

Luckily on newer version of Android there is always an option to quickly access the media volume after you press the volume button once, but it's still unintuitive.

Good news: iOS changed the default behavior of the side buttons: they always control system/media volume now. (Unless you flip a switch in settings.)

I've noticed the Chrome feature as well. I watch a lot of Twitch streams, and it causes a frustrating experience, albeit with possible workarounds by Twitch. It's that Twitch is about live streams and live chat, but now the video autoplay is delayed until I activate the tab, but chat is still live from the moment I clicked on the link. It basically buffers the stream now, but makes me go out of sync with chat. One alleviator could be Twitch adding a "go live" button that shows up when I'm not live.

There are still two classes of problems unaffected by this change.

1) As is popular with gifs, there could very well be multiple of these autoplaying videos on the same page, probably even multiple fitting in the same viewport area. If they had sound, these would interfere with eachother.

2) My understanding is that many listen to music from some source unrelated to the webpage containing these autoplaying videos. So even if there's only one video, its autoplaying sound could easily mix with my tunes.

Doing autoplaying sound is hard, but with gaze tracking and knowledge of system sound usage status, I think a pretty good solution is possible.

That is not an (at least exclusive?) chrome feature, since it happens on Firefox as well.