It's important to remember that in the age of big data and data aggregation, small pieces of information that seem inconsequential matter more when they're combined with others. The fact that this information is going to be collected doesn't just mean that someone is only ever going to be looking at the tiny pieces of data that are collected under this bill. This bill is adding to the amount of data that can be collected and aggregated with other information that's known about people.
Knowing, by itself, when someone comes in or leaves can be very useful information in a variety of ways, and it seems harmless, but it's very difficult to predict what any one of the organizations on either side of the border who has access to this information might do with it when it's combined with other things.
It's a hypothetical and general warning. We know that information when combined becomes more powerful.