It was introduced in May with the release of 5.2.4 which was also publicly tested for 4-6 weeks before release.
The feature is intended to auto pause the currently playing video or audio player when another is played which makes sense when you have audio overlapping.
It looks like something that has been missed by myself and anyone who helped to test the betas is the scenario of silent multiple videos or multiple Bloc video backgrounds.
I should be able to improve that in the next beta release.
This is good to know. I planned on having a home page soon with various two column feature blocs, but with autoplay silent video rather than images. It sounds like this would be blocked at present.
I removed this on the page thats using the 3 x videos and they are still not working.
I will send you the page in private as not able to share in public on it.
So I have managed to remove that code that norm pointed out (Thanks @Norm) and hopefully I can switch this when its updated so hopefully we can let a video know if we want it to play or autopause with other videos.
I have another issue which I will post on a separate post as its not related.