The "act as if you [have] it" really depended on your government's policy at the time. I live in the Netherlands, and during the height of the COVID scare here

The "act as if you [have] it" really depended on your government's policy at the time. I live in the Netherlands, and during the height of the COVID scare here and in the EU you needed e.g. a negative test taken days before every flight, before attending a concert etc. So even if the false positive rate was say 0.05% that's for each individual test. But that quickly adds up. I think I did on the order of 50 tests during COVID. If your spouse needs the same that's a 0.05 * 50 * 2 = 5% chance that one test during that period was a false positive. Which could be a relatively life-changing event, e.g. the difference between a nice holiday, and being locked up in a quarantine hotel for weeks on arrival. There were other ways those relatively small false positive numbers could cascade upwards, e.g. policies recommending that if anyone you've recently met had COVID, you should also quarantine.