9050 is a builtin default, from the Tor Manual...
SocksPort [address:]port|unix:path|auto [flags] [isolation flags]
Open this port to listen for connections from SOCKS-speaking applications. Set this to 0 if you don’t want to allow application connections via SOCKS. Set it to "auto" to have Tor pick a port for you. This directive can be specified multiple times to bind to multiple addresses/ports. (Default: 9050)
When you're starting it "from unix", it's probably looking for the default torrc, not finding any defined in the builtin default location (you need to specify the location with -f and optional --defaults-torrc if it's not in the location it was told to look when it was compiled) and instead falling back to it's default settings.