If the user who has created the sickness record for the employee has the System Owner role or the 'Salary Admin' permission, the sickness they are adding will automatically be approved as soon as they create it.
In this case, their name will also be displayed as the approver of the sickness even though the sickness hasn't gone through the approval process.
This is because the 'Salary Admin' permission enables them to override the approval process.
If you need the sickness to go through the approval flow you will need to advise the employee to submit their own sickness from the Self Service menu rather than adding it for them.