Captain Stable:
Add in extra words like "it's the" and you might be misunderstood - when transmitting, you don't hear how your words get to the other end. Did that crackle come just at the wrong moment? Will somebody else mentally fill in the gap incorrectly? Does inserting extra, unnecessary words actually HELP? Of course it doesn't. So why do it?
In general I agree with you but in my copy of CAP413 it states if you dont receive the full transmission uniterrupted you ask for it to be said again. ATC as professionals should be doing this not mentally filling in the gaps.