However, I can't contest the argument that you need English to understand the ambiguous wording of problems. I've had my fair share of frustration over the way some easy problems are worded.
Yep; I relate to your experiences of numerous ambiguous questions as seen in a range of textbooks. I often got the feeling that "revised editions" of maths textbooks were just newer books, perhaps with a few answers in the back amended, a more recent year stamped on the inside of the front cover, a more colourful cover, and expressions such as "Edition XX: with new improved XX" plastered over the cover (despite there not being much visible improvement).
However (maybe because I studied a LOTE foreign to me, and English Language), I found myself, in many cases, able to 'analyse the context of questions (if you will)'. I suppose I did this by reading the question over a few times and considering the most likely intended meaning of the question through some educated guessing as well as considering the intended the meanings of ambiguous questions I had answered in the past.
Although I cannot pin down the complete reason for my ability to better interpret opaque questions than my peers, I am quite sure I did have a significantly sharper mind in interpreting ambiguous questions when compared to some of my capable peers (who often consulted me about the ambiguous questions). I am convinced that studying the two aforementioned subjects gave me an extra edge in 'unlocking' ambiguous questions. Furthermore, I reiterate that past questions I had encountered must have been a large factor in helping me understand unclear questions.
I also acknowledge that:
- I don't really have any specific examples of ambiguous questions to discuss (so my argument can fairly be seen as weak)
- I have encountered a few (but not too many) ambiguous questions which I could not interpret and answer
- Ambiguous questions are not to be applauded as they are the result of poor writing (although some might argue it stimulates the mind xD)
- I can't really say that my interpretations of ambiguous questions were correct (I just realised this

); I simply wound up with the same answer in the back of the book. So I guess it's more accurate to say that I correctly interpreted the author's intended meaning?
- There is usually more than one 'correct' answer to such ambiguous questions
- You and I may have experienced totally different kinds of ambiguous questions (again destroying my argument). Btw, I used the "Cambridge Essential" MM textbook
- I did not do VCE English (I did Eng Lang, and only just realised this >_<) so maybe my argument is completely invalid..
- There is more to acknowledge
However, I've also had experiences in which peers had trouble answering unambiguous questions simply because "the wording was difficult". Thus I can safely say that proficiency in English is a prerequisite to proficiency in Maths (even if only slightly)
Just my two cents worth
TL;DR English may sometimes help maths