If the countries are trying to do contact tracing and isolated quarantines where flare-ups are found, it absolutely matters.
This is what people are talking about at the moment when they mention easing lockdown restrictions.
Imagine a single government trying to get the word out to everyone who may have come into close contact with someone who flies from London to Berlin on a Friday, jumps on a train at the airport, parties for 48 hours, flies home on the Monday and feels ill/gets tested the following Wednesday. Then replace Berlin with "Liverpool" and see how that improves things.
This is what people are talking about at the moment when they mention easing lockdown restrictions.
Imagine a single government trying to get the word out to everyone who may have come into close contact with someone who flies from London to Berlin on a Friday, jumps on a train at the airport, parties for 48 hours, flies home on the Monday and feels ill/gets tested the following Wednesday. Then replace Berlin with "Liverpool" and see how that improves things.