I have seen several wing chun guys fighting tournament they did very well and exposed the strong point and weakness of this fighting art. Fast offensive and counters to striaght attacks and weakness to fakes and circluar attacks from long range. These guys placed very high in most Tournaments they fought in, until they reached Mid-national level.
How could it be illegal? If you don't get hit, which is the purpose of a block. Hitting the person 1st is the key to point fighting, which is Wc strong point.