“Tests are invalid if you take them apart”

I’m a little confused, y’all. If I see two lines, I open the test to look and those same two lines are there, what exactly changed in the two seconds I took to open t??

In the cheapies it’s hard to see sometimes and opening it allows you to look closer is all. I understand cracking it open before it’s used but when nothing changes on the strip why is it suddenly considered invalid??