As described in the official Kinsta Blog I would expect the wp_get_environment_type() method to return development on DevKinsta websites.
A workaround is just defining define( 'WP_ENVIRONMENT_TYPE', 'development' ); within the wp-config.php file, but I would expect it similar to the Kinsta production and staging environments to be set automatically as this is easily forgot.
Q: DevKinsta Version
A: Version 1.0.2 (1.0.2.1256)
Q: OS Version
A: macOS 10.15.6
Q: Docker Desktop Version
A: 3.1.0