I think you shouldn't be so quick to discount what Brazil Boy's saying. Why do tall tulips have to be tall plants? I can have a group of 2 year olds, and say they are all tall, but does that mean they're all 6 feet tall? of course not. It means they are tall 2 year olds. So just because they are all tall tulips, they do not all have to be tall plants. You, in your response, just found the faulty reasoning when you asked "what is tall" The tulip *could* be a tall plant, or it could a small plant, just taller than other types of tulips. Be careful where you throw in that word *must*. It's not something to be taken lightly on the lsat.
Brazil Boy, IMHO, gave you the correct faulty reasoning.