The mandatory fines may be new, but the idea of searching phones isn't: It's part of Trump-era border control in the US. Went big last year when a US citizen working for NASA JPL (with security clearance and secured information that he was not
permitted to disclose to random US citizens like border control) felt compelled to give his password
(more here).
Though I hate the idea and am usually strongly against any infringements on privacy (yes, I don't like the "what have you got to hide" argument), I'm weirdly kind of in support of this. It just seems slightly inconsistent that border control has the ability to confiscate the physical phone, but not look at what's on it (though of course if they hold the physical phone they can probably get a lot off it without a passcode).
Having said all that, I do assume with any of these things that it will start off by giving officials lots of power and saying they won't use it, and then they slowly start using it anyway. But so long as "reasonable cause to suspect" continues to be adhered to, it is entirely sensible. And I would hope that they see no more mandatory unlocking than they currently have mandatory confiscation (which is hopefully just about never?)
Another interesting question with such things is "If they are able to collect and hold onto any of your data, who will be responsible for the loss of that data after the inevitable breach?" I'm guessing they would wash their hands of it, which is not good.