Generate RSA key in Ubuntu 20.04

Whenever I create a public/private keypair using ssh-keygen in Ubuntu 20.04, I get an OpenSSH private key file instead. Even if I manually specify that I want to use rsa using the following command:

ssh-keygen -t rsa

I still get the following for the id_rsa private key file:

-----BEGIN OPENSSH PRIVATE KEY-----
...KEY...
-----END OPENSSH PRIVATE KEY-----

Why does it say OPENSSH instead of RSA and does that matter?

It seems to only be an issue with Ubuntu 20.04.

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