Someone else will probably be able to answer this for you better than I. But, as far as i know; they only assign a name after it has been formally introduced. When it is a seedling; it is a number only.

Dahlias submitted to trial garden must have names or they are rejected. The names are only known by the trial garden director. They are planted in the garden with only numbers to ensure anonymity. The results of the judging is reported to the American Dahlia Society and those varieties that pass with passing scores are published in the ADS Bulletin in December. In the past, some trial gardens have printed some lists after the judging has been completed. This has not been the case in recent years. The policy recently has been to keep the entries anonymous until they winners are published.

In England, all entries are listed on a sign at the trial gardens and the judges can see the list before or after they judge. Probably this is better for the public but worse for the quality of judging.