Bathroom ceiling light LED retrofit
The issue is thermal... and we're fighting two completely separate types of thermal wars. 

The war on fire: Incandescent bulbs don't care about heat, they love it, they love being oven lights. They also create a lot of it!  A 40W bulb makes 39 watts of heat and 1 watt of light.   So with incandescent, the war is to keep the incandescent's heat from setting the building on fire.  A great deal of fixture design goes toward that purpose, including the lamping limits (e.g. 60 watts).  

The war on product longevity: LEDs and CFLs make far less heat.  A 40-watt equivalent LED (7W) is very efficient, it makes 1 watt of light and only 6 watts of heat.  However, LED and CFL must be kept cool. Their driver/ballast will have its service life shortened by excessive heat. LED emitters can burn out if not properly cooled.  (junction temp at the emitter must be &lt; 185-240F; the heatsink must be significantly cooler to move heat away fast enough.) 

So in a closed fixture, the war shifts from "preventing fire" to "keeping the lamps cool enough to last".  Certainly a better prospect! 

Presumably you will not want to fit LED bulbs brighter than 20 watts actual (about 150 watts effective) because it would be just too much light.   That means that thermal issues are completely off the table, and the reflector requirement on the label is simply not required anymore.  


That said, though: LEDs naturally emit light in about a 150 degree cone.  Most of the time you want a cone or a wedge, and this fixture wants exactly a 150 degree cone, which is a perfect fit for LED.   Therefore you are better off using a "PAR-style" LED bulb that simply places all the LED emitters in a flat plane aiming downward, and does not use inefficient reflectors at all.  


And I would go for one that is shorter than  your current BR30s, so it lights the diffuser more evenly. 

 [src: China, not one I'd reco, but this is the general idea.]

The bulb can be as simple as that: raw 5050 emitters arranged on a flat surface.  Don't buy an LED that has a PAR style reflector: first, reflectors are silly with LEDs, and second, that will give you too narrow a beam.