Unix has quite a bit of history, and a lot of things with historical roots.
Should questions primarily about the history of Unix be on topic?
I think it should be on-topic.
The history of any software can be used to understand why some part of it is the way it is.
I think they're fine as well, and this question made me think of a history question to ask, so hopefully we decide they're on-topic :)
I have no problem per-se so long as they're answerable.
I have been putting some history questions per-se as well. Please see Can somebody list the earliest public source-code repositories and when they opened? and if possible open it.