Sometimes artists use materials that are difficult for them to control. So, for example, using a very broad brush means your painting will (can not) capture small details but maybe that's OK or even desirable. So is it still art when the artist is just unskilled with the tools. For example, one day, some artist may discover a technique to capture fine detail with a broad brush. Now anyone using a broad brush can capture fine details and must choose not to (or choose not to learn how to). Does that change the quality of their art? Does it make a difference that they could have conveyed their intent more precisely? I don't think so.
Why am I suddenly thinking about art? I saw a poster for a band in Tokyo called "Bump of Chicken". I have no clue what was supposed to mean but that's not the point. Just because I and other native speakers know how to use English to create "fine detail", does that mean that someone else who only knows how to use it as a "broad brush" is wrong? If this was a public sign then I think the answer would be yes but it's not. A band's name is a (small) piece of art, not a means of conveying practical information and if the artist chooses a medium in which he is unskilled or which is difficult for him then I suppose the result is still legitimate even if it makes no sense to someone skilled in the medium.
So from now on, I'll look on dodgy English usage as abstract art.