Juliarugula I've also noticed the apparent discrepancies in the column designations for seed parent and seedlings.
Here's what I do: if a section has multiple listings of the same name, that has to be a seed parent section( e.g. Eillene C., Kenora Majestic, Pkg John S, Fancy Pants, Hallmark). Another strategy is to use the time period the Dahlia was released... Seed parent is likely the Dahlia released years earlier, e g. Hollyhill Black Beauty is the seed parent of Sandia Nocturne.
Even with the discrepancies, I find the information highly valuable! This morning I was finishing off planting my waterlily section and planted a Hollyhill Black Beauty in the waterlily section. That was based on the Boley's information, and @Teddahlia mentioning HH Black Beauty makes seeds.