I have an iOS device, but it says that I'm in an Android experiment in the blue border. How is that possible?

Because experiment segments are not only dictated by platform, if your device is paired and you are currently viewing an experiment, you'll technically be given that experiment on your device even if there are no relevant changes available

The only thing that defines an experiment as iOS or Android is segmentation filters, and that limits what you see in the shake menu or the variation switcher as well as what's delivered in production. Since setting distribution is the last step in the build process, we didn't want to limit your ability to connect to an experiment if you're paired, just in case you were planning on making it an iOS + Android experiment.