This is true if you only have a few, slow growing plants, but with a greater plant mass from the beginning diatoms will be less of a problem, even in low light set ups. That is why in a new tank stem plants are good to include along with the much slower growing Anubias, Cryptocorynes etc. With this strategy I have found that diatoms, even if they appear early on, quickly disappear as the plants become established.The biggest problem with low light tanks is that diatoms often will out compete your plants.