When starting up a site, the macOS notification will pop up stating that the site is ready to go ~3-5 seconds before it actually is. Trying to start the site shows a 503 error.
The notification should wait until all services have started up completely.
This is something that has bothered me as well and we fully intend on doing something about it!
Technically speaking, the green light and site started statuses are based off of the calls sent to start up the container and the services inside of the container. Local doesn’t wait for the services to fully start before showing that notification (or a green light beside the site in the sidebar).