Your may be right ...but the difference is the user enabling the option - that's how the driver knows.
Basically according to Eric Chan and others, finest detail forces the printer driver/printer to operate at 720dpi, whereas the default is 360dpi. While this might be beneficial for the sharp clean edges of vector graphics, it is not recommended for photographs and large images. It most likely has more to do with longer rendering times and memory issues when printing the file and not actual image quality. I've tested it several times years ago, and I couldn't ever see any improvement from enabling finest detail.
The challenge with any output is understanding and correctly applying output sharpening, so using finest detail after sizing to 720dpi and correctly sharpening may indeed be beneficial for some images, but using it without those steps most likely will accomplish nothing.
I'm not sure that my answer is on topic, but as a graphic designer, I actually know something about this. That Finest quality selection is for text(most of which is vector) or any other vector object, and YES the printer does know the difference. Vector elements aren't rastorized until the final destination is known and allows the post script processor to raster the vector elements to optimize their curves. With the finest detail I can print 2 point type legibly, without it 8 point type is so aliased it looks muddy. It may also have some resolution influence, I am not as educated in that area, but I can tell you that if I am seeing aliasing its not a resolution issue. It's a post script issue. InDesign has an option to "print as .bmp" which also turns off the post script processing, thus making text and vector images look muddy when there is fine detail.
I printed a page of business cards last night and forgot to make that selection, and the difference is night and day, no loupe needed.
My photography skills aren't sharp enough that printing at anything over 300dpi would display it, but I am fairly positive that the finest detail setting wouldn't touch your image. PostScript isn't a raster engine.