Tunick’s lawyers claim the agents “never read him his Miranda rights,”
irrelevant unless his statements are going to be used against him
I don't really see why this is an enormous civil liberties story. Destruction of evidence can, I think, legitimately be a crime even in a free and democratic society. It's not like they're trying to make the feature itself illegal... the main civil liberties complaint to have here is that searches of phones on borders are a thing at all.
Compared to https://www.thenation.com/article/archive/you-can-be-prosecuted-clearing-your-browser-history/ (from 2015 - 11 years ago, under the Obama administration!) where the person apparently didn't even know the government might be considering the deleted stuff "evidence", I find this story harmless.