You invite some of this when you write detailed and fixed requirements -- or when you make your solicitation process rigid and inflexible. If, for example, you don't allow the Service Provider to ask questions to better understand your requirements, or you don't allow open dialogue on specifics, the service provider will not be able to offer solutions that will fit your needs, even though they may not meet the "letter" of the requirement. If the service provider agrees with everything you require, they may be putting themselves in a position of offering something that is entirely outside of their skillset, or contrary to their internal architecture or processes.
So you should be wary when their response seems “too perfect”. You must be able to read critically, and ask the right questions to get at the real meaning of any proposal. You must read it as if you were listening to your teenager describe his latest outing with his friends: what is not said is often more important than what is said.