I would have thought so. Sheep were very much smaller before the intensive breeding programs of the agricultural revolution. Lambs would have been tiny, and you would have needed a lot of them to serve the typical Norman hall full of lords, knights and ladies. So waiting for it to grow a bit was a better bet. I suspect that they expected rather less sophisticated cuisine back then, and the amount meant more than the taste, not forgetting the ritual and status aspects of food- I doubt if anyone has ever really liked boar's head (not tete du sanglier or verrat). Modern French cookery only dates back to the late 16th century, when they imported it from Italy with Marie de Medicis.

It's also interesting that though the Normans introduced the rabbit (in its modern form), no one eats lapin, and perhaps no one wanted to eat chevre. And they cooked deer as venison, but hares didn't become lievres (though the little ones are leverets).