Technically, you are right. The "UV" diodes above 400nm are not UV, but that is how they list them and sell them on their sites, as UV leds.
I purchased and use the Exotic 430nm led for my "violet" supplement:
http://www.clay-boa.com/exotic-hyper-violet-led-430nm/
but you can purchase sub-400nm leds here:
http://www.ledfedy.com/products/1-500w-led/3w-led/c-71/
They have anywhere from 365 to 415...I installed and tested 395's and 400's to see what they did, and they did make the green pigments fluoresce more. However, I wanted to be more specific in targeting chlorophyll so I just went to the 430's and stuck with that.
Honestly there are a lot of specific spectrums on a MH bulb that are not available on any available LEDS, but I dont think that makes it better, I lean more towards the fact that it is wasting energy on those unneeded spectrums.
We have studies that have been done that show the absorption and emission spectras for pigmentation and fluorescence of virtually every coral in the hobby, along with the same for the different chlorophyll(s). I imagine if we target led fixtures to accommodate those ranges, with the ability to individually adjust, we can more efficiently provide the same benefits of MH, with the lower operating cost of LED, which is better for the pocketbook.