The Sonos software release notes are available here:

https://support.sonos.com/s/article/3521

My guess on a ‘dot release’ is some sort of bug fix to something in the original 12.2 release. It’s a rather common thing in software for those so called ‘dot releases’. No new features, just bug fixing. I have always assumed the same from Sonos. 

They've added support for some ios device (se g2, new ipad pro, latest ipod) maybe it was this

That’s 12.2 but thanks 

Yeah, wasn’t expecting features, just curious if anyone knew what was fixed. I heard of some people having new AppleTV issues after the 12.2 update, something to do with 5.1 or 7.1 

If you scroll down the page further you will see the other release notes for recent previous versions. HTH 

In 12.2 the LPCM codec was implemented for the Sonos Arc - this fixes an audio issue with Apple TV4 HD and 4K which uses that uncompressed format. It’s working fine here. I have seen some users were having difficulty with their PS4 but that looked to me like they were sending the audio in an incorrect format, rather than multi-channel LPCM. So that might have ‘possibly’ been related to the issue you read about, perhaps?

Well it still didn’t fix the Alexa issue where you ask her to confirm the volume and she says the same number every time you increase or decrease the volume.

I looked at the Release Notes - link below - day the update went live but it wasn’t and still hasn’t been updated. 
 

https://support.sonos.com/s/article/3521?language=en_US