You are right although as I understood it, the MS standard is exceedingly complicated, some would say in an attempt to "obfuscate" it.
In any case, this specific excel template states that it requires Excel 2007 and might misbehave if using any other program such as OpenOffice or Google Sheets:
> Please note that Microsoft Excel 2007 or newer is required. Other software like Open Office, Google Docs, and Numbers may import the Excel spreadsheet, but due to differences in the way they handle dates you should double-check that the calendars are correct.
In any case, this specific excel template states that it requires Excel 2007 and might misbehave if using any other program such as OpenOffice or Google Sheets:
> Please note that Microsoft Excel 2007 or newer is required. Other software like Open Office, Google Docs, and Numbers may import the Excel spreadsheet, but due to differences in the way they handle dates you should double-check that the calendars are correct.