Exactly. The corollary is you demo a pretty UI with no backend and then have to watch the crushing disappointment when you say it can't be shipped tomorrow and you need another 6 months to build something behind it.
Ouch, yes. I have been on both sides of both situations, and it just underscores the true value of a good dev team, and management who understand the process, both internal and external. I would say the management is arguably more important than raw dev talent, as managing expectations is paramount to all other output in most business.