Club naming isn’t the easiest thing as it’s obviously the first stage of your marketing. In overseas clubs it’s a bit easier as they have the history behind them. Many clubs were built off of geography and therefor had a chance to build up this identity before hitting the big stage. The geographical divide was built up from scratch and you almost had tribalism in force.
Sydney, especially, is a tough market with that. Sydney FC is already seen as the Sydney club and it has the money and organisation behind it to push this. The easiest and fastest way to create an identity, in Sydney, that sets you apart from the other clubs, is geography. Wanders did it well and didn’t limit themselves to one area. The West is as a small or as big as you want it to be. Limiting a club to just the “Macarthur area” would limit their potential market, having a term such as South West, opens up the market to people from outside the area.