Hi Vincent
I'm glad to help, that is what this forum is for.
Now, your doubts are, of course, based and logical, but I'll try to answer from ESIT's point of view.
A bit of background knowledge first
Furthermore, as you explained it above quite well, the interpreting techniques seem to be more important than the knowledge of languages.
Well, I have to nuance that. At ESIT it is more imporant to learn the technique, yes. But that is not because technique is more important than knowledge of language, it is because complete command of your languages is a prerequisite.
Languages are an instrument here, so you have to know them inside and out
before coming to ESIT and learning the technique. Essentially, all the technique in the world is not going to save you if you lack vocabulary.
The rest of what you say, particularly
What I mean is that if you do not master the interpreting techniques, you will not be able to work as an interpreter since these techniques are the same whatever the language combinations ...
is perfectly, unarguably true.
But consider this: there are two ways to get kicked out of ESIT
- Not mastering interpreting techniques.
- Not getting your languages up to level.
In the first case, if someone seems REALLY incapable of doing it, the teachers will say so after evaluation. And trust me, they do say it. But maybe someone just needs more time, not just the two years at ESIT, so why close all the doors? It's their time and money, they are not stealing it from anyone! (We are assuming that they have some other language up their sleeve, of course)
And in the second case, I already talked about alingual people and the like, but I didn't mention that there are cases when people would enter into ESIT with language combinations which are a bit too large for them. That is normally done after evaluation. I have a friend of mine, former ABCC, for example, who was given the option to pass into second year if she dropped her Spanish C. Another one, ABC, had to downgrade her English B to C, and since she hasn't got any reserve language to make ACCC, she got kicked out. But imagine that this person really improves another language and comes back. In that case it is not the technique that is lacking, it is a simple re-adjustment of languages.
The short of it: that rule was written essentially for language readjustments, and not for people who really don't have the mindset to be interpreters.
The perfect example of this was my AA friend who was kicked out, who is planning on improving her German and make a comeback as an ABC or ACCC.
That is ESIT's theory, but I pretty much agree with it.

Enjoy