Jan,
If I'm understanding you correctly, I think your question presupposes that there is only one possible way a sentence can be understood.
Language is not that precise. It's actually very, slippery.
In another thread, for example, you pointed out that the word, "Other" is not in the Greek text at Colossians 1:15-20, which is true enough, but by the same token, neither is the word, "Things."
All translators are inserting a word here.
"Things" and "All things" and "Other things" are all possible ways the word, πάντα could be understood.
I don't think there is any question that the NWT is favorable to the JW's by design. But in most instances, it is still well within the boundaries of definitions and grammar.