How old is the male? The same age? Is the pullet cooperating?
The mating ritual is not just about sex but is also about dominance. The one on bottom is accepting the dominance of the one on top, either willingly or by force. One way males impose their dominance on other chickens is to mate with them. On rare occasions a male will mate another male or a female will mate another female. That’s not about sex but dominance. Immature males are more likely to enforce this dominance than more mature males. That’s why a lot of immature males literally lose their heads. People think they are being brutes when they are just following their instincts.
It is a good sign, especially if she is cooperating instead of resisting. It’s also a good sign if the male is older and a true flock master instead of an immature adolescent. But this does not give any guarantees of egg laying. I’ve seen a 13 week old pullet willingly submit to a 13 week old cockerel and she did not lay for another two months.
Still, be encouraged. It probably won’t be long.