No the opposite is true - Python does not come preinstalled, but Ruby does.

    chrisseaton@Chriss-MacBook-Pro ~ % python --version
    zsh: command not found: python
    chrisseaton@Chriss-MacBook-Pro ~ % ruby --version
    ruby 2.6.8p205 (2021-07-07 revision 67951) [universal.arm64e-darwin21]

Isn't Ruby also included by default?

As mentioned in another thread: not anymore.