I've seen this mentioned several times here, but have not seen any corroborating evidence. That does not make what you have written wrong, I just like to see evidence from a known source.
The one thing that is definitely missing from most LED lights is sub 400nm light. I believe Orphec puts UV-A diodes in their lights as well.
Except for Kessils and possibly Orphek, I think you're right. Higher-end LED units like the AI Hydras and the Radions do actually have "400 nM" LEDs in the fixtures, but IMO, not nearly enough of them. In my case, I've Radion G3 Pros (both XR15w and XR30w). The XR30w has 10 watts of 400 nM LEDs out of a total of 170w. However, there's a sharp drop in efficiency of diodes in the violet range (400 nM isn't UV, despite manufacturer's claims to the contrary), so the radiometric output of the light fixture in the sub 410 nM range is poor.
That said, I started the LED odyssey with AI Color Vegas. I had very poor luck with them; very few stony corals of any genera would grow, and many outright died.
I switched to Radions about a year and half ago. The odd thing about them is that corals of the seriatopora, stylophora, montipora capricornis, anacropora, blastomussa, and tubipora (pipe organs) grow quite well. Acans and most acropora do not. Acropora, in particular, has been problematic. There's often odd color shifts in new colonies, uniformly poor growth and outright die-offs. Yet the same does not occur with frags of these same colonies under fluorescents of approximately the same PAR and in the same water system. There have been a few exceptions with acropora - a small handful of acropora species/clades have grown decently well under the Radions.
It's for that reason that I just pulled the trigger 20 minutes ago on an 8-bulb ATI T5HO fixture to replace the Radion over my 50 cube. While I definitely like the intensity variation and spectral shift over the photoperiod of LEDs, in the end it's about having a reasonable shot at growing everything that strikes my fancy, regardless of electricity savings, which I calculate to be minor at best. I suppose it'd be different if I had a 6' x 3' tank, but T5HO and MH bulb costs just aren't all that significant either compared to the overall cost of the hobby.
There's also an aesthetic consideration. This may simply betray my long-term obsession with reef keeping, but tanks lighted with LED only do not have the visual appeal of MH/T5HO or T5HO lighting on a tank. It may simply be the overall lack of green in most LED fixtures that screws up color rendition, but for me few things compare to a spectacular SPS tank lighted with 14k - 20k Metal Halides. So my new 4' tank build will be MH/T5HO unless someone convinces me otherwise.