Ah! That is an important clarification.
Wing Chun and Kali are very different systems, despite the fact that they look a little bit like each other at times and a lot of people combine them and/or do both. I think we have the alliance between Bruce Lee and Dan Inasanto to thank for that. I have no judgement or condemnation for people choosing to do both or combine that two.
But, you can't attribute things from Kali to Wing Chun. They are different systems, different approaches and different methods. I get why in a weapons system you target the hands/wrists and why you want to be out of range of something sharp and pointy, but the question I was responding to was about pak sao in Wing Chun.
In Wing Chun, you want to dominate their space. The "center" isn't their wrist or their elbow it's closer to their spine. I want my students' primary focus to be on getting to the person that has the hands attached to them, not their hands. We do occasionally talk about defending against weapons and we "spar" (if you will) with training weapons to see how that changes things and it certainly does a bit. But, I don't redefine Wing Chun around those scenarios.
I could say "if you were in a scuba diving fight like in a James Bond movie with mutliple attackers and one of them had a spear gun, you wouldn't be able to maintain your stance". That would be true, but it wouldn't use that point to redefine Wing Chun. When you get into rules based contests, the rules favor some techniques and discount or disallow others. If you participate in those contests, you have to adjust your approach accordingly, but that doesn't change anything about the system outside of that context.
No disrespect to FMAs, but they aren't Wing Chun and Wing Chun can't be explained through them anymore than they should be changed based on Wing Chun principles.
First let me explain what I mean by parallel. Most classes are 1/2 class WC, 1/2 Kali, they aren't taught at the same time, it's literally a Part I, Part 2 class. One day a week an instructor certified as a Provisional Master by Grand Master William Cheung teaches a "pure" WC class.
That said TWC is very similar to the Kali we study (unarmed) in that while you want to attack along your centerline to the opponent's centerline you do so from the blind side whenever possible. So a typical TWC entry will have me stepping in "jamming" him but (roughly) on a 45 degree angle. So both arts have "zoning" built in. Once on the flank the idea is that your attacks maintain that dominant position by taking their balance/center. If they maintain their balance, you zone again to their new flank.
In principle however the pak in either works as follows (again unarmed). In the pak sao drill you may aim for the wrist BUT in practice, action and reaction being what they are, you will naturally end up further on the forearm, so it is to get you used to the motion, nature of the contact, maintaining forwarding energy etc. The Master who teaches the WC exclusive class follows this method and he knows little and has nothing to do with the Kali training.
If facing a knife in Kali it is admittedly changed a little bit. Then it is more of a pass to the side rather than a forward along the centerline and is, largely, an "oh crap" maneuver because the last thing you want to do is be simply passing a blade, you want to be controlling the limb holding the knife until disarm (if unarmed vs armed, both armed, different ball game.)
So it's more a matter of one reinforcing the other. Aiming for the wrist in the stereotypical pak drill will likely in a real fight end up higher on the arm due to the dynamics of a real fight, also aiming for the wrist in that drill helps minimize confusion when you transition to the knife, the only mental gear that needs to be changed is the direction of the energy.
I should have been more clear but at work so took some short cuts.