Currently Proton Drive does not appear to create a version history for XLSX documents. That is a serious risk for anyone who stores information in this format, because all it takes is one erroneous save (or a ransomware attack) successfully syncing, and the data is gone for good. One major argument for cloud drive use is exactly the prevention of such a scenario and frankly, when you promote a product with a 10 year version history then it adds a bitter aftertaste when that version history does not cover one of the file types where you will most need it.

So please, stop exempting XLSX files from version history. Do version history for all files instead. Or change your marketing such that you clearly state that users will have a 10 year version history of their AVI, MP3 and OGG files but not for XLSX, so that they can make an informed decision.