I'd respond that a non-sport system in which you principally train to fight someone who fights just like you might not be adequately well-rounded.
If everything has to be right, it's not going to work. That it does work is evidence that pieces are not so weakest-link fragile as indicated here. It's great to strive for perfection but a bad idea to use a system that would require it.
We don't principally train to fight someone who fights just like us.
But the fact remains if there are gaps in your Chi Sau , that means there is a weakness somewhere in your defence and you will be hit.
It is irrelevant whether someone fights like us or not , what we are dealing with in Chi Sau are different types of forces , whether the force comes in straight like Wing Chun or circular from some other type of style.
Is the force coming directly at our center or slightly off center , we must choose the correct technique to counter that force.
Consistant training of the Sil Lum Tau form and the practice of Chi Sau will foster a habit of constantly keeping your wrists on the centerline and being in your stance.
This is why there is so much repetition in Wing Chun and we don't have a gazillion forms , the secret is to just keep your damn hands on the centerline and be in your stance.
Even crappy Wing Chun will still work to a degree , but if you want to reach the higher levels and attain effortless power then things are required to be spot on.
Near enough is not good enough.
As an example It wasn't uncommon when training under Yip Man for Sigung Tsui to just practice pivoting for five hours in order to find his center , just think about that for a second , can you imagine being in your stance for five hours pivoting 45 degrees from side to side.
Most people probably couldn't think of anything more boring , but it wasn't boring to him because he was concentrating on the details.
So if your just interested in smashing people in the face and being a bit more freestyle with your movement you can go and learn boxing or something else , but if you are interested in studying something that you will be trying to perfect until the day you die then learn Wing Chun.