Ok but think about this, when tracking an F2L pair during inspection, I already know what's going to come up and I don't have to look at that pair. When tracking it while executing your cross, you don't know what's coming and you will have to constantly have to look at that pair., Because I can just plan the F2L pair, I can just start looking for my next F2L pair while doing the first one. That also means that you can't even do your cross at full speed. When planning the F2L pair, you can almost every time.