Short answer is it doesn’t, the point of the development mode is the user controls it. PM2 is a service (or process manager) so it’s running the node application as a service. There are some alternatives like forever: forever - npm but PM2 has the widest feature range for things like built in node clustering, systemd and init startup services, user scoped services (so you aren’t running as root), ect.
PM2 => Production and staging on a server
The Strapi development is designed to be run manually by a developer locally