I'm a Sonos user and love it, but Sonos doesn't have any assistant capability at all, so saying "similar if not identical features" seems like quite the stretch.

Sonos just released a new speaker that works with Alexa (and I think others coming?).

https://www.sonos.com/en-us/shop/one.html

The basic Chromecast audio is $35 and has audio and optical out. That's a much better value than Sonos or the other competition. I already have those in multiple rooms, so this is attractive if I want to buy an integrated unit for an additional room that can also respond to audio commands. It fills a gap in the product line.

Expanding on that a bit - IMO a remaining gap is a Chromecast audio-like product with a microphone, that can take commands as well as play content through audio out. But I understand the market for that may be limited to people with expensive home audio setups.

Really, that would just be a Home Mini with audio output, and I suspect the Home and Home Mini don't have a separate audio output in an effort to make you upgrade to the "Max". Because frankly, you would be so much better off buying a regular Home and a $300 speaker setup than buying the Max.