Lab-grown diamonds can be tailored to exhibit the same impurities internal stresses, etc. that cause a minority of natural diamonds to fluoresce. This has not been a goal to date for synthetics because the highest price point is for diamonds that are most pure with least internal strain. If the economics of fluorescent diamonds suddenly become more attractive, I guarantee fluorescent synthetics will be on the market immediately thereafter, and will be indistinguishable from naturals without $100K worth of characterization tools.