By enabling the Disallow Approval by submitter parameter created the scenario like user one is submitting the expense behalf of user two then in workflow system throw error. And the workflow cannot proceed further.

Error Message:

‘’ Stopped (error): X++ Exception: Unable to continue. Submitter and approver are mapped to the same user Admin

at SysWorkflowWorkItem-create

SysWorkflowWorkItem-createWorkItems

SysWorkflow-save.

SysWorkflowQueue-resume’’

This Functionality is intended behavior of the product.