Since this is probably because you want to move contacts to another app like Mac Contacts,
It'e really easy to do this. Select them all, then drag and drop to a folder. Sort by kind because in addition to .vcf files, you will have .txt files for your groups. At that point, select all the .vcf files, drag and drop them onto the left side of
the Mac Contacts page, and let it rip.
I copied over 2600 contacts this way. It is correct you can't export to .csv, but that is because Microsoft has actually made it easier.
I'm trying to export my contacts from Outlook for Mac 2016 to Outlook.com and can't even do that. Yes, Microsoft to Microsoft.
I tried your work around above which is great for moving contacts out of Outlook for Mac to my Mac Contacts, but that still doesn't allow me to import those contacts from my Mac Contacts to Outlook.com
It seems the best solution is to spend $39.99 with some code writers in India that sells an app that can convert OLM files to CSV files for use across all mail platforms.
Needless to say, this is straight up ridiculous that Microsoft can't even convert its own OLM file to the format required to be used with another one of its own applications. Makes no sense at all.