The accounting department can use billing status to note when a job's estimate has been approved, when the job has been pre-billed, and when the job has been billed, paid, and closed. The production status doesn't interfere with billing status, so each department gets job reports their way. Both status codes are user-defined and customizable. Milestones mark key phases or steps in a job's lifetime, while status codes show the status of the job today. Traffic milestones are used for planning and balancing all of the shop's resources in order to meet all of the client's deadlines.
Milestones are forward-looking, while status codes only focus on what's happening today.
They're both useful when used together because they let production people see what the need to keep the work moving. No, all of the job tracking features work independently. Small shops typically use only job status reports and maybe milestone traffic reports. Tracking jobs by production status is the best place to start, because it'll replace the manual job log you've probably been keeping. If you keep up with job status as they change throughout the week, you're daily job hot sheets will be timely and accurate.