That method wont work on every chick--only certain sex linked crosses. However there is a different way to guess the sex using the wings. Pullets typically feather in faster than males, so chicks with long wing feathers are more likely to be girls--even if all the feathers are the same length. Males typically feather in slower than females--the difference is really obvious next to a pullet.
Long primary and secondary feathers--probably a pullet (in both fast and slow feathering breeds)
Long primary feathers, short secondary feathers--probably pullet for slow feathering breeds, cockerel for fast feathering breeds
Short primary and secondary feathers--probably a cockerel in both slow and fast feathering breeds
Since this method isn't the result of a specific sex-linked cross, it's not 100% accurate, but it is better than no guess at all.
Cochin bantam pullet at 3 days--notice the long primary and secondary feathers, and even some covert feathers growing
View attachment 2689882
Cochin bantam cockerel at 3 days--notice the very short wing feathers
View attachment 2689884
Those two are 4 weeks old now and confirmed pullet and cockerel by comb sexing.
Also, I vote May and Flower! Very cute seasonal name pair! I like Cinnamon and Spice too.