This is correct except the 0-2 months. Even if you accept dating a pregnancy as starting at the start of your previous cycle, these tests will be positive before your next cycle would have started. The typical “is this a positive test” is around 8-10 days post ovulation and a few days before their period is due. They’d get a definitive test 1-3 days later. So the period of “it’s positive but I can’t be sure” is something like 0.9-0.97 cycles into a pregnancy (again, with the weird dating from your last period’s start and complicated by the fact that most people don’t know ovulation dates & cycle lengths frequently vary).

If you’re well into a pregnancy, tests will actually start getting lighter due to how the tests work. It’s called the Hook Effect and can start happening around 5 weeks of pregnancy (https://www.captodayonline.com/Archives/0612/0612f_not_so_ob...).