My untutored impression is that both parties are correct. There is nothing in Japanese that prevents clear expression of ideas, but (more culturally than linguistically) Japanese does tend toward a degree of ambiguity.
A translator friend of mine, for example, when translating into English instructions for what to do in case of an earthquake in Japan, added various specific details that were not present in the original Japanese. Her Japanese colleagues were a little surprised and made comments like “Americans like to be so specific, don’t they?” She replied that knowing exactly what to do and how to do it could save someone’s life.
Which, of course, is true, and which demonstrates that, even in a circumstance where specificity is important, tolerating a higher degree of ambiguity is part of Japanese culture.
Is this a flaw in the language (or culture)? To a large extent the answer to that question depends on what you believe language is primarily for. West Tellurian (earth) people have for several centuries believed that language primarily exists for practical purposes. In fact they have more recently built their lives around the picture-story that life itself took form, or “evolved” on a purely practical (survival-oriented) basis. This they believe to be “science”; but to an outsider it looks uncommonly like a “mythologization” of their own cultural outlook.
Not all peoples have assumed either life or language to be primarily a matter of practicalities. Most people, in fact, have assumed that practicalities are a means to an end rather than an end in themselves. Which, when you think about it, makes sense doesn’t it? Practicalities as an end in themselves are rather like a sign saying “do not throw stones at this sign”.
So what is language primarily for? For Buddhism, as for Taoism, the highest function of language is to give us “hints” or “indications” toward that which cannot ever be expressed in words. The Tao that can be spoken is not the true Tao. The Zen koan does not attempt to put the Truth into words, but to open the mind to that which is beyond words.
This, by definition, is the highest possible function of language. In its lower, more everyday functions, it still has some of the same “connotative” rather than “denotative” function. We cannot truly describe music or the taste of food, or the feelings the sakura arouses in our breast. The subtle feelings that define us as spiritual beings cannot be fully expressed in words, but words can hint at them and evoke them. Whether we see this as the primary way of using language may depend upon whether we see ourselves as primarily spiritual or primarily material beings.
Has this any connection with learning Japanese? For me it has. I was discussing with a Japanese-speaking American friend the question of watching anime, and she said that turning off the (Japanese) subtitles was largely a matter of confidence and tolerance of ambiguity. The ambiguity here, of course comes from unfamiliarity with the language and the uncertainty of one’s ear rather than from the nature of the language or culture. When I spoke of developing a tolerance for ambiguity she said “the Japanese are masters of that”.
This interested me. While the two ambiguities are not the same, I think they are for me related to each other and to a third ambiguity: the ambiguity a small child must tolerate while learning language. When a small child watches anime, there are various words and concepts she does not understand. She needs to build up slowly from massive ambiguity to getting the general gist while being unclear about exactitudes. She has no first language to fall back on, so she can only understand as much as she understands.
I don’t want to get into the whole immersion argument from a language-learning point of view, but to me there is a subtle intertwining here of the process of learning a “second first language” (or in a way, a first first language, since English has never felt native to me) and learning to tolerate ambiguity from a cultural point of view. Modern English is probably the most materialistic language/culture in Telluria, which is probably why it has always felt alien to me.
Everyone has her own reasons for learning Japanese and mine (appropriately enough) cannot really be put into words. I am trying to find something. And I think tolerating ambiguity is going to be a part of that process.