To each major word we have assigned one meaning and have held to that meaning as far as context permitted.
Not only this is wrong as a statement of fact (there are scores of inconsistencies in the NWT, as in any other translation), it is also stupid as a statement of intention.
As any dictionary shows, most words do have several "meanings" (both synchronically, in different phrases and contexts, and diachronically, as a result of language evolution) and require diversified renderings into any other language.
To "assign one meaning" you would have to ignore the other "meanings". Which can only be done arbitrarily, by deliberately choosing to misunderstand in x % of cases.
Of course they mean "assign one English equivalent". But the result is coded text rather than plain English.
For instance, *consistently* translating nephesh or psukhè by "soul" results in hijacking the English word "soul" from its usual English meaning (the NWT "soul" doesn't mean "soul") and making it available for the sectarian "definition" (the so-called "biblical 'soul'").
(Bible translation is a good place to watch man's impossible desire to overcome language with language -- and its frustration.)