I find that students talk to each other and spread interpretations of the assignment. They might be correct, they might not - either way the interpretation spreads (never through anything like 'official' course forums set up for students to ask about interpretations, of course). They've also gone through shared experiences in other courses beforehand and will often simply come up with the same incorrect interpretation. For 5 years the basic assignment was clear and easily understood, then the next year it's almost universally misinterpreted. Those shared misunderstandings have easily outnumbered creative interpretations to help grades in my experience.