That's fine, but be transparent about it.
"Call screening won't be available at release at X, Y and Z countries due to (reason)." Or "This is a US only feature and we're working towards releasing it in more countries in the future". Something so they we'd know. Only way I found out is I purchases the 3XL, I got a call, couldn't screen it then had to look it up and found there was some random Twitter response from Google where they replied to a tweet asking if it'd be available in the UK and they said no it wouldn't be.
From the Pixel 3 presentation, unless I'm gravely mistaken, there was nothing to indicate it wasn't going to be available as a feature on the phone in certain countries.
Just really poor communication. They mentioned that night sight wouldn't be available at launch, they could have said call screening wouldn't be available in all countries at launch.