Most (but not all) white LEDs have a specific property: the LED itself is creating pure blue light. To create the appeareance of white light, a part of the blue light is then converted to wavelengths in the green-red region via a phosphor coating. But, especially in cheaper configurations, it still leaves a pronounced blue emission line shaping the spectrum like this:

    0
    0    00000
    0 00000000000
   0000000000000000

With some coatings, the blue line completely vanishes, creating a light distribution close to an incandescent lamp, but others have a very pronounced line. In the light (sorry) of the report, it sounds reasonable to require a certain minimum "spectrum quality" for lightbulbs beyond a certain power output.