As a former consultant at a company that built many mobile apps, I think that was the norm. Picking either platform and trying to get some traction both focuses your dollars and developer talent on one decent thing that you can iterate ~2x as quickly on (while the app and business are very small) until you figure what you actually want to build. I think this actually applies to many things. I've seen people pick Android or iPhone apps first based on target demographic, and you might guess wrong, but usually businesses have a decent guess who their target customers are, and it doesn't seem foolish to focus on a small set of customers first.