OMV5 has NOT been released, or did you see an official announcement of the homepage? Sourceforge simply shows the latest uploaded file, that's all.
I know but on the other hand I understand why people are confused. No offence (as I really like your work), but you have to improve your communication.
On https://www.openmediavault.org there is absolutely no info about what version(s) are up to date. On the news page there is a OMV 6 teaser and some 4.1 news. Aside from that NOTHING ... no info. People who are used to the debian 'testing - stable - oldstable' scheme must think that OMV 5 is the most recent production version.
When you then visit the official download page (https://sourceforge.net/projects/openmediavault/files/) OMV 5.0.5 is the newest version that is not marked as beta. I understand why you want to wait for the release of Debian 10.1 but I really don't understand why you didn't append 'beta' to 5.0.5 when OMV5 is not officially released yet.
The result is - as you can see - that the 'unreleased' 5.0.5 has way more downloads than 4.1.22. The only place where OMV 5 is clearly marked as 'under development' is the Forum.
I'm not sure whether this confusion is even intended to attract more testers. In any case, that's what happens right now.