I agree, it varies so much from line to line, especially when we're talking malinois, where there are SO many different lines. I find alot of working people try to breed them larger than show people (alot of breeders throw some GSDs in the woodpile to accomplish this). Weight depends more on substance than height.
I have a 22.75 inch groen female who is 48 lb, and I have a 24 inch male who is 62 lb (I think he'll mature more between 65-68 lb). His sister is 23.25, expected to mature around 50lb. My dogs aren't tall, but they are substantial and therefore tend to weigh more than the dogs we see who are taller than them. There is another breeder I know personally whose males tend to range anywhere from 26.5-28.5 in, but they are considerably lighter than my dogs because they don't have the bone or chest that my dogs have.
On the other hand, I had a little 21 inch groen female who was never more than 17 or 18 lb at a good weight. She was very fine boned, and though she was only 1.5 inches shorter than my other female I had at the time, she seemed a great deal more petite. She was completely different lines.
My 22.75 inch female is heavier than a 24.5 inch male I had years ago.
So, it really depends on the lines. Females from one line can be alot heavier than males from another line. Some dogs may be very tall, but dogs 4 inches shorter might be heavier. Mals have such a wide gene pool that it varies considerably.