That's what is bothering me - the idea that ANY hen has to be small in order to be a good layer. I have not yet decided if that is one of those observations that were made that really had some validity across all breeds, or if it was just a strong opinion but only factual in very specific situations. Sometimes those old books have stuff that sounds like old wive's tales that turn out to be true and other times the stuff is way off base. But you still have to weed through things and see if it applies to your flock.
Our breed is large, over 5 lbs for females. We have differences in individuals as well as in groups depending on where we obtained them from. We have one group that we know was pushed for egg production. More of them lay every day with great consistency than any of our other groups. However these guys that lay better are too small for their standard and smaller than the other groups by comparison. They also have a number of other breed standard flaws too. We will not even sell culls because they are too far from the standard and I don't want someone backyard breeding them thinking that they are good representations of their breed.
So I'm not sure if the small size on them is what really helped them be better layers than the others, or if it is just coincidental that they turned out to be small. One of those things to make you go hmmmmmm.
That implication would not be accurate necessarily. There is a correlation on some level, but all links are not links of necessity. Links can be made, and links can be broken. Feed efficiency is the largest advantage that smaller breeds have concerning laying. The larger breeds often did as well during laying trials, but were left behind because they ate more feed. It is true that laying strains tended to be lighter in weight. Then, they were not selected for anything else.
Hogan saw a connection between breed size, metabolism, and lay rate.
Hogan had a lot of brilliant ideas, but we have learned a lot about production genetics since then. There are main points that may be useful for us today. It is in reality, more of a culling method than a breeding method. Breeders should be proven by their performance, and by the performance of their offspring.