It's standard. All people who are taken aside by customs in the US are given a standard form which asks for all passwords and keys for all devices they own. This is so they can immediately use the content on them to reject you from the country. It's presented to you in such a way that you are to believe you have no option but to fill out the form. You're offered the ability to talk to your embassy, but are told that is a useless opportunity that won't get you anything of value.
Since no one is explicitly saltating it, this only applies to non-citizens, right? What's the process when a U.S. citizen is "taken aside"? I would categorically tell them to fuck off. Do I face jail time instrad of refused entry?
US citizens can't be denied entry. They can, however, have their devices seized upon entry, and can enter the country, only to proceed directly into custody, whether CBP or someone else's.
In general, a US citizen can be detained for some time, interrogated and searched in an unpleasant fashion, have property they carry with them seized, and be subjected to (illegal, but it happens regardless) retaliatory prosecution under nuisance-type charges for being uncooperative or for being perceived to challenge the authority of the CBP employee, but cannot be denied entry to the United States.
But you can get added to the no fly list, which is effectively the same thing, as no carrier will take you. (You have to fly to e.g. Canada and cross at a land crossing.)
What I don't hear anyone in this thread talk about is, what happens if you present them with a blank device? Say I have a brand new chromebook, no logins, no data. Brand new phone, five emergency contacts and no messages. No logins. Brand new google account.
Won't that look pretty suspicious to mr. wannabe Jack Bauer in the TSA?