Yes! If they do not know what you are looking for, they shouldnt be looking.

I assume there are probably a 1,000 people that cross the US border a year where there is a very compelling case to check a phone. The same argument does not work for 10,000,000 people. So, I assume when you ramp up the people your adding have a much lower threshold than the old group.

Further there is a long history of random inspections as people cross borders without a warrants meaning it's simply doing the same things with different means. Basically, border security is one of the core functions of government and the expectation of privacy is minimal.

Or put another way, if you are going to open 1,000 laptops a year then I assume that getting a warrant would not be difficult. If you want to open 100,000,000 laptops a year then your not acting on any kind of evidence just going fishing. But, that kind of fishing tends to be ineffective and expensive both directly and by discouraging people from visiting the US.

PS: The same argument exists in other areas. Having 100 H-Bombs on ICBMs is a very powerful threat. Having 10,000 H-Bombs on ICBMs is just more expense without really changing the threat. You increase the risk of bad things happening, spend ~100x the money and gain what exactly?