In these specific instances I agree with you. The few I looked at were just single or no post communities. I think the mods just want to give these a chance in case anyone actually does want to take them over and breathe some life into them.
In general though, I think it’s healthy for the fediverse to have options, even with similar topics. I’m sure you might recall situations on Reddit where people didn’t like how a sub was moderated, so some people would set up r/TRUEwhatever.
they settled on that in 2014 so seems unlikely