Migrations are possible only to sites that are part of Stack Exchange; if you see a question migrated on a site you don't know, that is surely part of Stack Exchange.
Not even moderators can migrate a question to a site that is not part of Stack Exchange. What moderators see when closing a question is something similar to the following screenshot, which has been taken from Drupal Answers, where I am a moderator.
The question you are referring has been migrated from Super User, not Stack Overflow.
There is an overlap between Super User and Ask Different, but questions about Apple devices, such as iPhone, iPad, iPod are off-topic on Super User, and on-topic on Ask Different.
Super User is for computer enthusiasts and power users. If you have a question about …
- computer hardware
- computer software
- personal and home computer networking
and it is not about …
- videogames or consoles
- websites or web services like Facebook, Twitter, and WordPress
- electronic devices, media players, cell phones or smart phones, except insofar as they interface with your computer
- issues specific to corporate IT support and networks
- a shopping or buying recommendation
… then you're in the right place to ask your question!