In Business Configuration you set your own Sales Phase configuration and doesn't use the standard values provided by SAP.
Inside the application, the Sales Phase field dropdown displays only your custom sales phase as expected, however in the Server Side Outlook side panel the dropdown for Sales Phase is showing all values, including those standard from SAP.
SAP Cloud For Customer
The dependent picklists are not fully supported by the add-in.
This is the standard behavior of the system.
An alternative option may be to check the SAP Customer Influence Site to submit an idea.
Sales Phase; Server Side Add-In; Groupware; Side Pane; Sales Cycle; , KBA , LOD-CRM-GW-SRV , Server side groupware intergration , Problem