Horseshoes and hand grenades
Trevor Ewen

Totally agree, but with the caveat that literally anything could become a large unknown in a world where you can’t trust your platform/language/operating system/hardware/cloud provider to get everything 100% right. Acknowledging this properly, I think, just means emphasizing that estimates are estimates, not promises, and could go wildly wrong for reasons that are not your fault and not even in your code base. If you are doing something less than providing a closed system with formal specifications on every piece of code (and every piece of code that that code relies on) proving that the implementation is correct, then these sorts of things can and will happen given the opportunity.