No they do not hardcode paths, they just have to use some other mechanism (for example: registry) to find each other's location. MacOS doesn't really work this

No they do not hardcode paths, they just have to use some other mechanism (for example: registry) to find each other's location. MacOS doesn't really work this way either, half the apps available use installer and have their files somewhere in /Library. The time when applications were universes by themselves ended in 1990 with OLE.