The customer confirmed all of our hypotheses! We're awesome! I mean really, who wouldn't want a square disco ball? Let's go build it!
In the unlikely event that your revolutionary new product, the square disco ball, is actually a customer need, the customer will still challenge your expectations of what the product should be with either:Pricing discrepancies - "I would've paid more than $2000 for that." Unexpected use cases - "This will make a great piñata!" Marketing material miscommunication - "What is this disco thing of which you speak?" Ridiculous feature requests that no one else will want - "Why doesn't this disco ball come in a nice plaid?"
If you take the time to talk to customers and learn absolutely nothing new about your product, even if only a few random brainstorm ideas, then you probably were talking to not with the customer.