What exactly is a synopsis for? Mechanics aside, what do you look for in one? How does it help you, and the editors you send it along to? Obviously not as a writing sample, since no one can write a good one, and it can't convey much if anything about character, atmosphere, etc. So I'd imagine it is to give you a sense of the plot. But can you tell from the synopsis whether the plot is likely to hold up?
Lucienne Diver, who is a very good agent, once said "synopsis tell me if aliens arrive out of the blue in chapter 12". I thought she was kidding. She was not.
Synopsis tell you if the plot fails. It gives you an idea if the requirements of a genre are met, or played with in an interesting way.
Synopsis, when they are well written, give you a sense of character development and where the plot turns. Badly written, they tell you "what it's about" but not why you'd want to read it.
I have synopses for all the books on my list. When I'm placing projects, I read the synopsis before making a sales call. When you're shopping five books at the same time, details like names can get jumbled even in Miss Snark's well organized mind.