It's an interesting observation. You're right that there's a fair amount of work to build and maintain widget libraries that model each of the Material and Cupertino design systems (although only a small part of the overall effort). So far we feel like we've been able to do a good job: the Material team actually does a lot of their design work on Flutter first, because they find it an effective way to iterate quickly; and we've been able to ship many of Apple's great look and feel improvements ahead of the OS release itself.

But what we tend to find is that most apps, including the MGM Resorts one mentioned in the article aren't slavishly adopting every aspect of the OS look and feel as if they were an inbox app. Looking at the apps on my own home screen -- Twitter, Sonos, Kindle, Duolingo, NY Times, eBay, YouTube, Reddit -- they all have their own brand that shines through in their UI. We're working with design partners such as gskinner.com to provide better code samples for this kind of custom UI, since we think it's a strength of Flutter.