Nextcloud asked in a poll at https://mastodon.social/@nextcloud@mastodon.xyz/115095096413238457 what database its users are running. Interestingly one fifth replied they don’t know. Should people know better where their data is stored, or is it a good thing everything is running so smoothly people don’t need to know what their software stack is built upon?
People don’t care and/or haven’t looked at the serverinfo page. That actually mentions the type of database in use.
So the “I don’t know” option was probably just the easiest.