If I recall correctly, Chen Zhaokui actually wrote two books, one on Yilu and one on Erlu. The books had not only detailed descriptions of the moves, but also something like 600 applications between them. I know my first teacher, Liang Baiping, has a copy that he was always intending to translate in his retirement, and there's a guy in Houston (Cheng Jin Cai) who's basically made a career out of having those books and using them as the basis for his super-secret taiji cult.
From the little bits of translation I've seen, this is not that. Liang Baiping is more fluent in English than many (most?) native speakers, and I know that when he translates he tries more to get the flavor and intent across rather than just doing a literal word-for-word translation. But in comparing the two, even aside from the omission of applications, the structures are a bit different in terms of how the moves are broken down, so that's why I don't think this is the same text as one of those books.
So then I wonder, if Chen Zhaokui was already writing his own books, why or where did this dictated version come to be?