EF trying to map SqlGeography instead of DbGeography when using ExecuteReader

Question

Why the Entity Framework binds the same field of Geography type with two different types (SqlGeography and DbGeography) based on way of retrieving data?

I recieve an exception when trying to read data by ExecuteReader

The specified cast from a materialized 'Microsoft.SqlServer.Types.SqlGeography' type to the 'System.Data.Entity.Spatial.DbGeography' type is not valid.

Here is a table:

CREATE TABLE [OneGeoField]([Position] [geography] NOT NULL

And data:

INSERT INTO OneGeoField (Position) VALUES(geography::STGeomFromText('POINT (30.5047009495918 59.862826902743)',4326))

EF generates a class for this table with DbGeography type of Position field:

public partial class OneGeoField
{
    public System.Data.Entity.Spatial.DbGeography Position { get; set; }
}

When retrieving data with SqlQuery method it works fine

var query = "SELECT * FROM OneGeoField";    
var list = db.Database.SqlQuery<OneGeoField>(query).ToList();

But in case of using ExecuteReader, it throws an exception

        try
        {
            var cmd = db.Database.Connection.CreateCommand();
            db.Database.Connection.Open();
            cmd.CommandType = CommandType.Text;
            cmd.CommandText = query;
            var reader = cmd.ExecuteReader(CommandBehavior.CloseConnection);
            var objectContext = ((IObjectContextAdapter)db).ObjectContext;
            var list = objectContext.Translate<Core.OneGeoField>(reader).ToList();
        }
        catch (Exception ex)
        {
            throw;
        }
        finally
        {
            db.Database.Connection.Close();
        }

Is it only solution to have a different model for ExecuteReader, and another for common approach?