Zero downtime upgrade

Docs (https://github.com/kubernetes/ingress-nginx/tree/master/charts/ingress-nginx#upgrading-with-zero-downtime-in-production) are mentioning that by default during an upgrade there is a service interruption caused by pods being restarted, and another article is linked with explanation how one can fix that.

But when looking at values.yml I can see both terminationGracePerios and preStop hook is set correctly in order to drain connections.

https://github.com/kubernetes/ingress-nginx/blob/a7fb791132a0dee285b47d0041f4f9acf1e7cff8/charts/ingress-nginx/values.yaml#L237

https://github.com/kubernetes/ingress-nginx/blob/a7fb791132a0dee285b47d0041f4f9acf1e7cff8/charts/ingress-nginx/values.yaml#L583-L587

Is the documentation a little bit outdated or there is something else that I should set to get near zero downtime upgrades?