I just watched the video and I must say those people were the epitomy of muscular tension and seemed to use some very convoluted actions.
Not a whole lot of deflection going on there , you could hear the hard blocking coming through on the video.
The problem with hard blocking and being tense as was shown on the video is that not only does it slow you down and waste energy , but it also offers a conduit to which your opponent can effect your balance and stance.
Any type of tension , particularly in the shoulders can be taken advantage of and basically used as a handle to have a direct link to your body , as you could see in the videos there was a lot of body movement in the stance as the heavy blows came in because the arms and the shoulders were absorbing all the force instead of the force being taken down to floor.
A lot of that force could have easily been neutralised with a Bong Sau and a bit of pivoting
All that energy has to go somewhere and it was taken on one point and straight into the shoulders
Being relaxed in the arms and shoulders is a must , in order for the incoming force to be directed down through the stance and into the floor
This hard way of dealing with force is very limiting , because it's basically two blocks of wood hitting each other and who ever has the the biggest block of wood wins.
When you see people who are very good at Wing Chun neutralise heavy blows , what you tend to see is that the body itself does not move when the force is absorbed , or if it does it is turned as one unit to dissipate the force.
This is due to mainly two things , a good stance but also the proper use of deflection.
In my opinion a couple of things have to be adhered to in order to make correct use of Wing Chun deflections.
- Unlike hard blocking , don't take the force on one point , spread the impact along the forearm.
- Stay relaxed so the arms and shoulders can act like shock absorbers , don't be like the two blocks of wood hitting each other.
- Maintain the proper angles of the arms so they don't collapse under heavy force .
- Use the correct timing so that as contact is made with his attacking limb , your deflecting limb is already in motion so that it can spread the force of the impact up the arm.
- Wing Chun deflections generally use the principle of a circle to dissolve force , and this is done a couple of different ways usually simultaneously. We have our arms scribing a circular path from our shoulder joint to redirect force either vertically up or down , horizontal , or diagonal.
- At the same time we have a much smaller circle operating as our forearms themselves revolve in some deflections so as to spread force along a wider surface area of the arm.
- Finally we have the whole body turning as a circle in the pivot , and when coupled with the other above methods can be used to turn away an incredible amount of force.
Some times the "softer" WC is not an option. 
