if a fan is blowing the leaves it strengthens the stems, it also so keep the leaves supplied with fresh c02
This members advice is correct,the advice you got to not let the fan blow directly on the leaves is not correct.
There are many benifits to having a fan blow directly on the plants,as allready stated it strengthens the stalks so the buds wont pull the plant down,fresh co2 across the leaf surfaces is another benifit allready reported.
Other major benifits include spider mite control ,mites as well with other aphids do not like windy conditions,mites live on the bottom of leaves & if the conditions are too windy they cant get a foot hold to attach to the plant & they die out.
Mold control is another huge benifit to constant air flow directly on the plant,fresh air is second to ozone in its ability to fight mold,its hard for mold to grow in areas where there is a conatant flow of fresh air.
In tight areas with restricted air flow " your closet " a single mold spore can wipe out the entire harvest,if a spore lodges itself within a bud new pistils & calyxs form around the spore,since there is no fresh air blowing over the mold spore it can be encased inbetween new bud growth,then you have bud rott which is like a greyish blue puss like substance that ruins all it touches.
The best defense against pests & mold is fresh air,as well as stimulating the plant to build thicker stalks.
In my grows i try to have all leafs blowing in the air flow at all times.