Leaf tissue tests that determine sex a week or two after germination have been around for years, and they work by detecting the Y chromosome marker from a tiny punched sample. The cost per plant is the catch, since it adds up fast on a twenty seed run compared with just waiting for preflowers. A cost comparison and a note on the few labs still offering the service are available at https://breederregularseeds.com. For a tiny grow with expensive seed it can be worth it, otherwise patience is free.