So that article tells me that there are differences between the 4D56 and 4M40 injectors, but I don't see a major different spec between 4D56 injectors. Those part numbers follow different formats, so I am hesitant to say that the "0" in one corresponds to the same thing as the "15" in the other, though it does appear that the ND-DN15PD6 part number corresponds to a 4D65 engine, not the 4D55/56. So it seems to fall under the general category of just get the correct parts for your engine? Denso makes nozzles for these motors, so there's nothing inherently wrong with that. IIRC then one of us (me or my dad) rebuild a set of these injectors using the Denso nozzles.
If it was an injector for the wrong engine then that's another story, but then there is the matter of these low pressure pintle-type injectors and how limited manufacturers are with their design. These things are not like high pressure direct injectors like in Cummins or Cat; they are very simple, very low pressure design, not to mention they just screw in to the head, so there is no way to index them for different spray angles.
Although I suppose that may be a misunderstanding on my part. Are you saying that these nozzles have different spray angles relative to the injector body, or are you saying that these nozzles have different angles of spray pattern?