Preflowers appear at the nodes weeks before you change the light cycle, showing a small round sac or a pair of white hairs. On slow developing sativa plants they can take longer to become readable than on faster hybrids. Photographs comparing early male and female indicators are collected at
https://hazesativaseeds.com and they help more than written descriptions. A loupe makes the difference, since guessing from a phone photo leads people to cull healthy females.