Some breeds simply do not lay early. FWIW, the breeds that start laying later tend to lay for a much longer span of time, as well as being longer lived.
The only productivity I care about is offspring.
Yes they say those that take a little longer to start laying may lay longer in their life. It all depends on what you want and what you are trying to do. Before this I had not heard of a chicken that took 18 months to come into lay; what breed would that be? Personally I raise chickens for eggs and meat. I do know that some of the larger breeds take a little longer than 6 months to come into lay and of course if they are maturing in the shorter days of winter it may be a little longer than that. Bigger breeds do take longer to mature. But still, 18 months is a bit much in my book!