SSIS changes SQL Server source data type from date to WSTR
You are using SQLOLEDB.1 which is a pre-SQL 2008 version of the driver (and deprecated), and the date data type was introduced in SQL 2008.

I suspect the provider isn't detecting the data type as it should, and you should probably switch to the more recent SQL Native client provider.

To illustrate this point, I created an SSIS package with OLE DB connection managers using both SQLNCLI11.1 and SQLOLEDB.1. The Data Flows will both use a  query of SELECT CAST('2017-02-27' AS date) AS DateType;

Looking at the metadata, we see SQLNCLI correctly determines the date datatypes



The SQLOLEDB is unable to determine the date datatype and falls back to the "safe" type of unicode string