The Gatsby-powered website looks different to the canonical Ghost

The themes are slightly different, but I like the canonical Ghost more:

The former has been deployed to Heroku using SnathJr’s ghost-on-heroku, commit 2b9802, while the latter has been deployed using a fork of the official gatsby-starter-ghost, commit 31daf8.

Do the websites look different because the Gatsby starter uses an older version of Ghost? If yes, how can I update it?