There is some validity to that, in terms of preferring native species over exotics. But natives can't always do everything we want. I buy other things with attention to how much I think I can manage watering. However, even natives need extra support until well established.

I don't really approve of people growing lawn grass or water-intensive vegetables in arid zones. Fudging things a little is usually fine, especially if you landscape to conserve water (e.g. mulch, swales, guilds).