You are correct, this sort of thing has been happening for a while now. Who was POTUS Oct, 2016? It's an issue now because Orange Man bad.
In October 2016, CBP airport agents denied Canadian photojournalist Ed Ouentry into the country, after detaining him for over six hours and seizing his three cell phones. According to Mr. Ou’s ACLU attorney, “When the officers returned the phones to him several hours later, it was evident that their SIM cards had been temporarily removed because tamper tape covering the cards had been destroyed or altered.” Similarly, in July, CBP airport agents detained U.S. citizen and Wall Street Journal reporter Maria Abi-Habib for an hour and a half. When they asked for her cell phones, she refused and referred them to the newspaper’s lawyers. Fortunately, the agents eventually released her without seizing or searching her devices.
https://www.eff.org/deeplinks/2016/12/law-enforcement-uses-border-search-exception-fourth-amendment-loophole
Here is what the Obama DOJ wrote in 2014
https://www.justice.gov/sites/default/files/usao/legacy/2014/11/14/usab6206.pdf