The project page/readme gives the following installation command:
composer create-project drupal-composer/drupal-project:8.x-dev some-dir --stability dev --no-interactio
AFAIK know --stability dev is redundant when a dev version is selected (as drupal-composer/drupal-project:8.x-dev). Redundancy is bad because it's confusing (for people trying to understand the command/Composer) and it makes the command unnecessary long.
I would have created a PR removing --stability dev but since very competent Composer people must have written the readme, I thought there is some reason for keeping it in after all ....