Whether to use the author name with numeric references when describing a particular study
There may be slight differences between fields (I am in the chem-phys-mat. sci triangle), but the short answer is no, you do not need to explicitly name the authors. 

Stylistically, the "the work in [1] proposed" sounds rather forced and exactly as long as "Smith et al.[1] proposed". Note I am not a native speaker, so I have no clue what I am talking about. On the other hand I would definitely would leave the name out if I am talking about the same work over and over. Also, if you structure your statements like "This problem has been approached using this [1] and this methods [2]", giving the name is actually more awkward than leaving out. 

I think it also improves readability. Compare "our method outperforms the name-of-the-method method [1]" with your examples (name-of-the-method: you explicitly name what is the main difference). Assuming that the reader do not know the reference list by heart, this kind of reference is more explicit and more informative than the other two.