The first almost 2 years of his life were a struggle to get him to eat anything, he was so underfed, but he was always visually healthy... he wouldn't eat kibbles unless I mixed it with other crap, he's tried every kinda food there is, even The Honest Kitchen (which he LOVES now) was a slight struggle once the novelty of a new food wore off.... but for some reason having Lÿka around, he's turned into the cookie monster, he goes crazy when I bring his meal in, his food drive is thru the roof... I mean, he's the kinda dog that people told me "take away his food after 10 minutes n starve him till he eats right" n he would rather not eat for a week than give in to hunger... but now, if I walk into the room with his food bowl n make him do OB before he gets his food, he sits in heel position making whining noises begging for his food. I don't know if it's an age thing, or because he's watched a high food drive dog do backflips for her food n something clicked in his head or what.... but the thing I learnt thru all of this the most is "if he looks healthy, don't worry about how much he eats".
As for a smaller GSD... I will never go back to a larger GSD... I was a little disappointed at first when I realized Cujo would never be a big 85+lb GSD monster, but since then my attitude has changed alot, smaller GSD's have less structural problems, less bone problems, less health problems overall, longer lifespan on average, more agile etc.
If you really specifically wanted a 90lb dog n your breeder led you to believe that you would get a big 90lb dog, and by 12 months old the dog doesn't look like he's gonna fill out to that size (by 12 months the dog is about adult size minus the bulking up), then sure complain if you like --- I have 100 complaints to my breeder, but I never voiced any of them, because at the end of the day, I love the dog I have, he turned out to be a good dog regardless of my total ignorance to selection testing or lineage at the time, n if I were to get another GSD, I would look for the smaller sleeker breeding in hopes for another 65lb 24" tall male.