User is trying to change the class of a parent project, but it does not affect the existing time entries of the phases.
This happens because when you change the class of a parent project in Projects > General > Billing Options, Core prompts you to apply the change to existing time entries, expense entries, invoices, and payments of that project only. Then you get a subsequent prompt to apply the changes to the phases and sub-phases. If you select Yes for this prompt, Core updates the class for the phases and sub-phases, but does not update it on their existing time and expenses. It only applies to new time and expenses of the phases. In order to apply the change to the existing entries, you need to change the class at the phase level itself. In that case, you get the prompt that allows you to change it for the existing entries. Check the Core Help for more details.