Tested the issue on mac 10.13.3 using latest canary #69.0.3463.0.

Attached a screen cast for reference.

Following are the steps followed to reproduce the issue.
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1. Navigated to url: https://twitch.tv/
2. Observed that the video autoplayed with sound.

Note: The behavior is observed from M-60 builds.

hinoka@ - Could you please check the attached screen cast and please let us know if it is the issue being observed from your end.

Thanks...!!

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	853333.mp4 2.9 MB View Download

Hi correct, this is exactly the issue.  One more piece of this bug I didn't see in the screencast is that I have this flag set in about:flags (screenshot attached)

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	Screen Shot 2018-06-18 at 11.16.17.png 76.1 KB View Download

Thank you for providing more feedback. Adding the requester to the cc list.

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot

Tested the issue on chrome reported version# 69.0.3461.2 and on latest chrome# 69.0.3464.0 using Mac 10.12.6, Ubuntu 14.04 and Windows-10 with steps mentioned below:
1) Launched chrome reported version and enabled autoplay policy to "Documented User Activation is required"
2) Navigated to url: https://twitch.tv and observations are as follows:
From M-61 to M-65, when navigated to URL: https://twitch.tv, video got auto-played and audio is in mute condition and 
from M-66 to M-69, when navigated to URL: https://twitch.tv, video got auto-played and audio also got plays with sound.

As multiple behaviours are seen from M-60 to M-69, hence marking this issue as Untriaged for further inputs from Blink>Media>Autoplay team and requesting someone from Blink>Media>Autoplay team have a look at this issue.

Thanks!

Isn't that because major sites are whitelisted, hence Youtube still playing by default?  I imagine Twitch is big enough to make the list:

https://www.blog.google/products/chrome/improving-autoplay-chrome/

"If you don’t have browsing history, Chrome allows autoplay for over 1,000 sites where we see that the highest percentage of visitors play media with sound. As you browse the web, that list changes as Chrome learns and enables autoplay on sites where you play media with sound during most of your visits, and disables it on sites where you don’t."

It lets a lot of crap through.

Autoplay for Twitch is likely allowed because either (1) there is no browsing data, and Twitch is on the default list of sites where autoplay is allowed, or (2) there is browsing data, and the user has trained Chrome to allow autoplay by playing media with sound during most of their visits.

Closing this bug as it appears the policy is WAI.

Should the flag be renamed to "Documented User Activation is required unless on whitelist?"

"Documented User Activation is required" seems like a misnomer if it is conditionally applied.

Renamed summary.

 Issue 857559  has been merged into this issue.

A better solution might be a control in chrome://settings/content that enables the user to choose whether or not to allow video to play - period.

There have been instances when I've attempted to read an article, and there were two or more third party video advertisements that auto-played [thankfully muted] - consuming so many resources that even scrolling down the page was painfully slow.

Just want to say, just because I play media with sound during most of my visits doesn't mean I want it to autoplay.

 Issue 893774  has been merged into this issue.

I agree with comments 11 and 12. Users keep asking for a way to disable autoplay and when they are given a control that is advertised as doing that it should, in fact, do that. 

No website should be automatically whitelisted. 
I want no autoplay at all. 

Why won't you give that option to your users that keep desperately asking for it?