Why Does Bak Mei, Lung Ying , Southern Mantis , and Wing Chun use Bil Jee Sao

[FIRE HAWK]

I have noticed that other Chinese arts like Bak Mei , Lung Ying Mor Kui , Southern Mantis , use a technique that is in Wing Chun called Bil Jee Sao or Darting fingers , is there some relation as to why these other systems use the Bil Jee Sao or Darting Fingers ?

[yuanfen]

The structures and engines of those arts are quite different from each other- so the bil jee similarity is primarily in appearance.
Just as most arts have a "kuen" but each kuen is different-
on formation, on positioning. in delivery, in strategy and tactics.

Joy Chaudhuri

[Phil Redmond]

Even Karate other arts have finger jabs. In Karate it's called a "spearhand".