That’s correct, none of the Sonos devices can be used to connect with a phone call. 

wow wow.. that is unbelievable… my Google Nest Hub which I got for free from signing up my Internet can do that...

It may be an issue with the Sonos, or it could be a feature that Google holds back from third party devices in order to sell their own. We don’t know, but I’m happy you already have a device that can fulfill this need for you. 

Personally, I’d prefer not to see voice call capability on my Sonos devices.

What would happen if someone calls me when I’ve got music playing throughout the house to all speakers? Would they all “ring” to notify me of the call, or just one of them? Would the call then be grouped to all speakers, or just one? Which one? If I chose to take the call on just one speaker, could anyone with a controller group another speaker to the one on the call and eavesdrop?

The software development to cater for all these types of situations, and being able to select them according to household preferences for different calls/callers seems quite extensive.

The Sonos Beam is a voice enabled speaker. It doesn't purport to be a full Amazon Echo or Google Assistant device. I am surprised at your surprise. 

Google Assistant branding unfortunately brings along the expectation that it can do everything a Google Home or Hub (or a competitor) can do.  In the end, it is just the voice assistant part.  All the other features that come with the expectation are different technologies that don’t live under the Google Assistant umbrella.