In a perfect world with a perfect grow light, all leaves would look "black" to us. We see green, because the plant does not absorb/use green, it reflected it. The "blurpuple" funny lights are great for hydroponics, because they do not produce colors the plants do not use. All the T5HO fixtures are not designed for "cages". They are designed to hover a few inches over a 12-18" industry standard grow tray.
And there is also marketing and markets. Home growers are not growing food to sell at the maximum efficiency. Home growers typically want to "see" their plants because it is a "hobby". They want full spectrum so what they are growing can look as lovely as possible. They might even be growing hydro roses and other "inedibles".
Finally, ALL THESE LIGHTS ARE FAKES, both LED and florescent. You worry about what your chameleon sees? A T5HO full spectrum bulb only puts outs dead center red,green, and blue. It does not put out orange or pink or brown. The thing between our ears and the thing between the chameleons not ears, interprets the 3 RGB spikes as "white". Same with the LEDS, though the single white ones are starting to put out "a little" light inbetween RGB, but for the most part its still just the RGB spikes.
But at the end of the day, it really doesnt matter much. The magic 6500k everyone shoots for, that just mimics the 1 hour a day at noon during summer. Outside of that window, it could be 3000-9000k depending on the time of day and time of year