at the risk of boring everyone, the formula "I don't believe in x" is an expression. You are right that those phrases are not literally true, but then neither are mangers usually "moving forwards" (they're usually sat on their fat bums), and there isn't really a box of thoughts in the first place, never mind any stray thoughts outside it.
So, Brocolli, you are not really correct to think of demonstrating any existential truths to these people. But you would be correct to wonder why they can't just say what they mean, without the use of a tired cliche.