I agree with you HalilG,
but upgrading Nginx during WordOps upgrade create a risk of failure which can cause all sites to be down. And I do not want users to stay on an old WordOps release only because this risk of failure exist.
To update all server packages without overwriting any configuration, there is the command :
wo maintenance
Then to update stacks and their configurations there is the command :
wo stack upgrade --nginx/--php/--php73/--netdata/--dashboard