One of my former bosses once accused me of being too honest with the customers
Never bring engineers to customers*
Usually the boss 'forgot' to inform everyone of the latest agreements and you'll end up with the engineer pointing out something that will not work. Let the folks with the sales smarts handle stuff. And put on that confident smile
*: I'm ofc joking, but my boss had a hard time keeping his mouth closed at a customer site - standing right next to our COO and the customer. You could hear him mumble something like 'this is shit, it ain't gonna work'