A good change in theory, the policies have negatively impacted games and other experiences (according to The Verge) that use the Web Audio API. Pallett is advising developers to update their code based on Google's recommendations before that time.
The new policy, introduced in April, was created to "intelligently" block unwanted video from playing unless you had either white-listed the site or previously interacted with it. For some HTML5 games, users could re-enable audio by interacting with the game's canvas via a click-to-play interaction.
WebRTC applications are also affected by a range of issues caused by Chrome 66's autoplay policy, including no longer playing an incoming call sound, broken audio visualizers, and no sound coming from remote peers. The new autoplay rules blocked audio that played on its own as soon as the user opened a website, however, this change broke countless online games and apps that used autoplaying content for legitimate purposes.
Meanwhile, the implementation delay is created to give "Web Audio API developers (e.g. gaming, audio applications, some RTC features) more time to update their code". The team here is working hard to improve things for users and developers, but in this case we didn't do a good job of communicating the impact of the new autoplay policy to developers using the Web Audio API.
Pallett urged developers to prepare for Chrome 70 by following its autoplay instructions for the Web Audio API. As others have pointed out, this is a non-trivial user interface challenge with a lot of nuances. He added that the change wouldn't stop Chrome from silencing most websites' autoplay videos and audio.