I more inclined to think you got flagged for SSSS based on something else, e.g. sharing a common name with someone they look for or meeting any other criteria which is used to profile for "person of interest" like last minute bookings, booking one-ways, paying via anonymizing payment instruments etc.

I suppose they do not like to give away their methodology to make it easier to avoid it and also not to run into some trouble like "oh, TSA is doing ethnical or racial profiling - let's raise hell". So they make up a story about nationality and residency which is just BS but no one will actually go and complain about it.