Build 4.5.0.91 of xlsgen adds the option related to updating formula specs whenever there is a row or column insertion or deletion.

By default, formulas in the workbook are updated to reflect the new rows or columns, and doing this keeps the integrity of the spreadsheet. But sometimes, depending on your scenario, it may be needed to keep the formula specs intact. That's what you can obtain by setting False to a new property we are making available at the workbook level, i.e.

workbook.FormulaDefinitionUpdate = False