Effectively, this is what it says in the site you mentioned, which I recently read.
"MP3 Skype recorder v. 4.43 works with the following Skype versions:
- Skype app is a version for Windows 10 only. Tested with Skype version v.12.1815.2100.0
- Skype for desktop. MP3 Skype recorder tested with latest version 18.104.22.168
- Skype for business"