The question clearly requires some operation in Android, either setting up new android profiles, or using a particular software. Is questions about android apps not on topic here?
That one seems a bit borderline to me.
The reason used, "Questions which are Android-independent...are off-topic..." is technically correct. I'd expect that Instagram in iOS would act the same way.
But it's also not like you can go to the website and create an account; you can only create an account by installing the app.
So I think the question is fine here, even if the answer is probably "you can't".