yes this is true it helps. but large amounts of nitrogen added to the soil creates imbalcne and the soil becomes addicted to it so to speak. the best thing is to encourage the growth of healthy bacteria in the soil. these bacteria are what fix the nitrogen and carbon in the soil and create healthy balance of nitrogen, oxygen phosphorous etc. a good rotting mulch is a source of healthy soil organisms.
i have never used nitrogen indoors in the shallow trays that most grow wheatgrass in, have you? does it work to defeat mold?
personally i think the answer to mold is good drainage, moist but not wet soil, and a healthy growing medium. i wonder if the shallow trays encourage mold growth due to short roots that have no where to go so they grow in on each other in big wads and that traps moisture which eventually causes mold. i don't know just a thought.