I just spoke with Apple Support and they told me it only works between 2 or more HomePods. Isn't this different than what they announced?
According to this article, the iPhone needs 14.2
HomePod 14.1 update brings support for intercom (Updated)
Alongside iOS 14.1 and iPadOS 14.1, Apple today released new 14.1 software for the HomePod. This update includes support for the new Apple Intercom feature andwww.homekitauthority.com
I’m not on the 14.2 beta so I can’t speak intelligently to that but it does work great for me, HomePod to HomePod, on 14.1.I have 14.2 and it’s not showing up under home settings at all.