It's a good question...but no you are not right to think that.
If something comes with a guarantee it will very clearly say e.g ''Guaranteed to work'' the reason there is such a clear disclaimer here is because much of trust 'theory' is very compelling and appears to make a lot of sense on many levels.
Anyone who reads any kind of information and takes it as truth because there is no dis-claimer needs to re-evaluate their capacity for critical thinking. ~ In other words a man or woman should always do their own research and gather as much information as possible from as many viable sources as possible coupled with the idea that 'to gather information in itself is not the end goal. Learning how to handle and decode information is much more important than the information itself'
I hope that helps.