Seems like new host and platform requirements have changed according to doc published on Dec. 1, 2017 here https://learn.microsoft.com/en-us/office/dev/add-ins/overview/office-add-in-availability
We were told in a report from the MS Seller Dashboard to use add-in commands and make it compatible with Excel 2013, iOS Mac and the iPad.
However, according to the doc above by Microsoft, add-in commands are not listed for Excel 2013 and iOS.
The add-in availability Chart is gone https://dev.office.com/add-in-availablity
Therefore, what are the new testing criteria for the Excel add-in for Office 365?
All Excel add-ins submitted to the Office Store must be compatible with Excel 2016, Excel 2013, Excel for Mac and Excel Online, unless they are using APIs unsupported by one of these clients. See Specify Office hosts and API requirements.
Your add-in is only required to support iPad, should you opt in during the submission process. See Develop Office Add-ins for the iPad.
Since February 2017, all Excel add-ins must use add-in commands. In Office 2013, your add-in won't display add-in commands, and uses the value of SourceLocation to run your add-in as a single task pane add-in. See Step 2 of Create add-in commands in your manifest for Excel, Word, and PowerPoint.