Must not need it? None of my phantom DE ballasts have them either.
Correct. A fan allows for a smaller form factor. Holding all things equal, a No-Fan option requires a larger housing and/or perhaps heat sinks or fins to dissipate the heat at the same rate a fan would do.
I feel like the answer is going to be just market hype unfortunately...
It usually is.
My biggest vexation is when someone makes yield claims and/or asks me how much he/she will get per light.
One thing is to evaluate and compare a driver [ballast] and a whole other thing is to compare/contrast between lamps. One drives the other, but they are still separate multipliers in the end product: light. And light-- together with--Nutrients, Air, Temp, Cultivation Style, Tools, Cultivators skill, Genetics, etc, all together--correlate to yield.
To associate yield to a single product type, or even worse, to a brand, is extremely lofty and ambitious and will most likely be inaccurate.
Though I have always been ferociously skeptical about yield claims, I must happily admit that I do remember when the indoor 1-Lb/light barrier was broken.
Then the 2-Lb/light barrier was broken.
Now recently 3-Lbs/light being a norm in commercial facilities. Seen even higher grams/watt yields in trick SOG applications.
Clearly not all due to improvements in just lighting gear. It is due to improvements in *all* the factors that contribute to yield.
This is all a result of the industry maturing, learning, and naturally improving.
The Diamond "thumbs-up". <should crack a smile>
Good times.