Newsletters tend to have a regular schedule, are easier for consumers to get started with (everyone uses email already), and have revenue models that can make it sustainable for the creator.
Whichever servers you contact to do not initiate the connection, you do.
But the technical distinction between the two holds. If you subscribe to an RSS feed and then never launch your reader again, nothing happens. If you subscribe to a newsletter and never check your inbox, your inbox still fills up.
Everything is just a feed, email, RSS clients, social media, messaging apps, notifications channels. It's just a matter of managing which ones you make a habit of visiting and being notified about.
The local RSS reader you never launch is not executing. It does nothing - does not pull content. Nothing happens - no bits are transferred over the wire, nothing is written to disk until you initiate the pulls by launching the app.
Email servers operate continuously, so that when some publisher sends ("pushes") an email, that is delivered to your inbox, which will eventually fill up your quota (or the disk).
You can blur the distinction of what happens from the user's perspective all you like, and that's why I mentioned marketing phrasing. But it does not change what is actually happening.
The technical distinction between the push and pull is about who initiates the connection to transfer content.
For further reference, I recommend https://en.wikipedia.org/wiki/Push_technology .
There's also the newer variant, PUSH IMAP. I think that one speaks for itself.
None of that is polling.
A primer: http://www.newbietechtips.com/2013/07/pop-vs-imap-and-push-m...
They have chosen to subscribe, you can contact them. You don't know your RSS subscriber count. It is a more highly engaged group, easier to build a relationship with.
And the number of people using RSS compared to using email who would consider a newsletter subscription is tiny.