I cannot reproduce the issue you reported.
Here is the example I used to test it out:
The source data is from a CSV file:

A Modify Fields node is used to auto-detect and convert the data type of the fields. The data is then sent to an Output Excel node that is configured to use a Template file (and one that is not using a template file).

The Output Excel node configuration properties are shown below:

The OutputSpec property value is configured to route the data from the (first) input pin of the Output Excel node to the second worksheet in the output Excel workbook.
The Template xlsx file has two worksheets. The second is a default worksheet that will store the data that is loaded into the file by the Output Excel node (it is named Raw_Data).
The first worksheet had format definitions for the required cell ranges and the values for those cells reference the cells in the second worksheet:

When the data flow is run, the output workbook is populated with the data and the first worksheet contains the formatted data.

See the attached zip file.
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Adrian Williams
Precisely Software Inc.
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