Another political 'feel-good' move
So, on paper it sounds good. The agency can stand before the press and laud the important new safeguards put in place to protect American citizens' rights and privacy.
Except: the exception. "If officers have serious concerns about a traveller but have no time to get a warrant, they can seize the electronics and later apply for a warrant retroactively. If the warrant application fails, all the information harvested must be destroyed and may not be used in further prosecutions."
The "serious concern" is purely in the mind of the officer, as directed by guidance from the officer's supervisor. This is a rather flexible provision that can let matters proceed 'as per usual' with little change. As for "information harvested must be destroyed," of course it will. Except for that auto-transmitted to the federal data repository in the Utah desert.
As for applying for a warrant, we the citizens have become all too familiar with "rubber stamp" warrant approval arrangements in US courts.
Trust. Once lost, nearly impossible to regain.