man: we need to be more careful with the unit search paths we document
We generally document the suggested paths, not the paths possible in weird, non-standard setups. We do this in order to not confuse administrators/users unnecessarily and to push people to install things into the same directories on all distributions. We are PID 1 after all, the really basic building block of the OS. Unlike for an app there's very little benefit in being entirely relocatable.