This is the furthest thing from the truth.
In Wing Chun in China there are seven main wing chun families with many off shoots.
There are many different stances in the Wing Chun system.
The two predominate stances are 50/50 weight distribution and 70/30 or 60/40 weight distribution.
Some wing chun styles start from a front stance, some from a neutral stance and some from a side neutral stance.
A lot of wing chun stances step heel first and some step toe first.
I personally believe you must always have 50/50 weight distribution. Then, you are in control of your balance and you will be able to utilize interrupt ability. If your stance is not 50/50 in weight distribution you will be deemed off balance and over committed to a certain direction.
For example. If you have most of your weight on the back leg, it will be very difficult to move backwards. Similarly with the front leg. All the weight or some will make it difficult to move forward.
A philosophy of Wing Chun is to always assume your opponent is bigger, stronger and more powerful.
In Combat there is always the unexpected. So balance and speed is paramount. So when you are 50/50 you can interrupt your movements when something unexpected happens.
Also, with balance and speed you will produce Power.
Sifu Garry has had this debate with many a practitioner that leans on the back leg. They always state that “we do not step back”. This is a very impractical statement to make. Obviously, these people have never been confronted by a 120kg African or very large person of any nationality trying to harm you.
A car cannot have a head on with a truck and survive.
If someone large attacks you, you can step to the side if quick enough, but most of the time situations occur to quickly and stepping to the side is not an option.
Therefore, you must make space and step back. If your stance is 50/50 you can accomplish this with the minimum of ease because you are not over committed or off balance.
Traditional Wing Chun also has the “Exchange step” which enables a practitioner to take a full step back while the Assailant is half stepping. This will create space for you to change direction and counter successfully.
Too many Martial Arts practice techniques in class but cannot use them is self defense, but pay heaps of money to learn impractical self defense.
Always remember. If you practice a technique in class, you have to be able to use it in a real situation, otherwise you are wasting your time and developing a false sense of security.