Can anyone explain why global works better than local for certain Pitch blocks?

[Atmospheric]

Brand new FX8 owner here. I wanted to create a preset with a pitch block that I could define to be -1 (on X) and -2 (on Y). I read the threads about putting a Volume block in parallel. Interesting technique. But a couple of people also had good results setting the source to Global instead of Local. I too found that effective. Why is that?

 

[mr_fender]

Global tracks the pitch using the signal at the grid input, so it is the clean guitar signal. Local instead uses the signal at the input of the pitch block. If the pitch block is placed after a high gain amp or drive block, the signal will contain a lot more harmonic content from the clipping and that can mess with the tracking.