Why shouldn't we change the values in the system status for work orders?

The six system statuses — Not planned, Scheduled, In progress, Completed, Posted, and Canceled — look like a standard customizable list of values. They are not.

The system logic depends on the values

A number of automated processes are triggered by these statuses. Posted generates an invoice and creates actual values for time and cost. Completed converts products into customer assets and adds a travel fee. If you change the values in the option set, the system loses its connection to this logic—and the error often only becomes apparent when something is not invoiced.

Do this instead

If you need more detailed tracking, create custom substatuses for work orders. They are designed specifically for this purpose, are linked to a system status, and allow you to distinguish between, for example, “waiting for parts” and “waiting for customer” without changing anything the system depends on.

If it's just the wording that feels off

If the problem is that “Posted” is not the term your staff use, an administrator can edit the labels without changing the underlying values. This changes what users see while leaving the logic untouched. That is the difference between changing a label and changing a value—and it is worth explaining that distinction to everyone who has access to customization.