I read the article again (thanks), and I also interpret the article as saying that wireless audio sync should work with speakers connected by Bluetooth to Apple TV.
However, this does not match my experience, and it does not match what Apple support say - they said wireless audio sync worked for Bluetooth speakers when connected to a TV that is connected by hdmi to Apple TV, and not my situation.
I will try Apple support again to see if I get a different answer
I would also like to know if anyone has successfully used wireless audio sync for speakers connected by Bluetooth to Apple TV
here are the steps I have taken:
• update Apple TV 4K
• Link Apple TV 4k to bluetooth speakers
• When I navigate menu system or play movie, sounds is coming through Bluetooth speakers, but with lag
• follow steps for wireless audio sync, page link is above
• on step 4, tone plays through speakers connected by hdmi (not Bluetooth speakers) - this seems like a bug, Apple Support assured me that this is the right functionality
• again, when I navigate menu system or play movie, sounds is coming through Bluetooth speakers, but with lag