The latest version of the Gutenberg plugin, 17.8, includes basic grid support. This version of Gutenberg (and this feature) won’t be in 6.5.

Gutenberg Plugin Gets Basic Grid Support
Grant M. Kinney @ make.wordpress.org • 1 year ago
Grant M. Kinney @ make.wordpress.org • 1 year ago
The latest version of the Gutenberg plugin, 17.8, includes basic grid support. This version of Gutenberg (and this feature) won’t be in 6.5.