Why a Bi-Polar/Non-Polarized Capacitor in vintage wahs?

[Effectsiation]

I'm just wondering if anyone knows why they specifically used a bi-polar/non-polarized electrolytic capacitor in the wahs of old. I would think that the originally specified value (4uF) is more important than having a bi-polar cap, if it's installed correctly. That's why I took Madbean's suggestion for the Sprague despite its relatively high cost for a single electrolytic capacitor. I noticed that in the BYOC wah, they opted for a 4.7uF NP. That choice seemed puzzling to me, and that's what has sparked my question. Is there some outstanding property of non-polarized caps that would be worth the .7uF difference (not including 10% tolerance) between these two?

I know some wahs also used a 3.9uF tantalum capacitor in that place, can anyone really comment on the importance of value vs bi-polarity vs material in this part of the wah circuit?

I know that wah mod sites say "Lifting the earth connection of the 4.7µF (in reference to a Vox V847) capacitor will cancel the wah effect and leave you with a volume pedal."