Dependas on the farm. there are some farms that produce master peices while msome produce crappy flowerhorns. Were to you think the big koked ones come from? a farm.
that's not true. Only true or lower quality parents. I've seen batches with mostly big heads from big headed parents. Big headed FHs arent even rare anymore.
If you breed flat head bloodline to big head bloodline, then that low percentage would be the case.
It's not always 1-5%. It varies alot. You can have the whole batch with head potential if you have the right parents for that. Then you gotta raise them right to get the big head also.
But what about everything else? The big head is the main trait but other traits you want from a low head parent will make you sacrifice some big head gene.