Hmmm...I don't think they have to lay eggs before going broody but couldn't say for sure.
My buff orps, araucana, ameraucana and silkies all are excellent broodies. Easter eggers are not known for broodiness, but I have a couple that like to sit probably because of the ameraucana in their bloodline.
I have had buff orp pullets lay one or two eggs and go broody. They can be very frustrating and very determined girls. The araucana tend to like to gather a clutch then sit. Silkies and my bantam ameraucana will go broody on one egg and fight to keep it. LOL
Jody