They probably do that in parallel, the point of the visitor disclosure isn't to reveal the social media history, it is so even if the social media history itself, which they have through technical means, doesn't reveal any basis for exclusion, the failure to disclose parts of it (which comparing the disclosure to the records they already have identifies) can do so, as well as pointing authorities to what the visitor thinks needs hidden and should be investigated further.
At least it's some evidence that the NSA, nor Zuck/Musk/whoever other fuckwit can provide the information...
Nope, only that it’s easier to perform a forced search than to us pre-existing secret search.
You think the NSA is competent enough to have that easily cataloged?
The problem with secret surveillance programs is you have to be “read in” to have access. No way they’re making that available to every border control agent. That’s why the interdiction programs at the southern border are handled via anonymous WhatsApp groups.
It’s way easier to just do the illegal and unconstitutional search at the border.