Atom and RSS are functionally equivalent despite their technical differences. Effectively no one has ever implemented Atom push capabilities so Atom is primarily only ever used for syndication. The term "RSS" is just a generic term for "XML syndication feed".

Atom push is actually implemented. SWORDv2 (but not v3) is based on Atom Push, and https://en.wikipedia.org/wiki/SWORD_(protocol) lists a few implementations.

My employer maintains a SWORDv2 server, and we have a handful of clients pushing to us; most of them are not listed on that page.

As an example, feeds available on every github repo:

https://github.com/EFForg/privacybadger/commits.atom

https://github.com/EFForg/privacybadger/tags.atom

https://github.com/EFForg/privacybadger/releases.atom

Google (Blogger, etc) pushes Atom feeds. Weather blogger is still relevant is up to perspective.