Suppose police kill 1 person per month across the US. That's would not be a huge red flag for me, but if police killed 10,000 people per month across the US that's grounds for a revolution. The ground between A and B can be vast, so saying X happens on it's own is less important than the context.
All I am saying is that a 3x annual increase in X can be a bad sign even if the old and new rates are justified because the trend on it's own is concerning.
In the United States, border zones are any areas up to 100 miles inland from a land border or coast. The majority of US population and cities are in border zones and the border rules apply to them:
https://www.aclu.org/other/constitution-100-mile-border-zone
Or to quote your link: Border Patrol, nevertheless, cannot pull anyone over without "reasonable suspicion" of an immigration violation or crime (reasonable suspicion is more than just a "hunch").
Consider what happened to people that showed up at Ellis island. Some people would be forced to strip, take a shower, and undergo medical examinations. Remember, this was published as perfectly reasonable things that confirm to social norms. Further 1-2% of people where deported often due to physical deformities. https://books.google.com/books?id=OyL6JatN5KwC&pg=PA129&lpg=...
PS: I don't mean we should go back to a system like this, just crossing borders is very meaningfully different than sitting at home or driving down the street.