salve, Harumoto
you have posted the thread into a "Theory and Principles", so i will try to give a theoretical "
yam yeung like" answer, ie. non black and white opinion.
you know that i really like techniques like
fo jin cheui,
po paai sau or
chau da cheui. you can use them pretty well to solve most of the common street fighting scenarios (pushing, puling, punches to the face, football kicks, low kicks, attempts to grapple and wrestle, baseball bat swings etc.), of course with proper footwork and body movement (and pwer and speed and courage - se below), so, why do we practice other stuff, too?
it is said - "learn a lot, practice selected few, and master one". the key to succes is imho in specialisation within the universality. everybody is different, what works for me will not work for you or your classmates; situation may also differ every time - one time you need a cannon, another machine gun is a better choice. you are not going to box with a boxer, or grapple with a grappler, so you have something in your arsenal in all 4 main types of attacks, ie.
tek da syut na - "kicks, strikes, throws, submission" and you have to train different situation drills.
from another point of view, and for Hung kyun very important, different techniques are just different tools helping us to drill how to use different types of power properly. techniques are limited (and in no way you will be super proficient in let us say 50% or 25% of all Hung Kyun arsenal), skills (courage, power, speed, distance, footwork, body movement... ) developed by practicing different techniques are universal. there are things i really did not like couple of years ago, and now i wonder how perfectly they work for me.
hope it makes sense a bit