Lens: converted 24-72mm f/2.8-5.6
They mean equivalent 24-72mm f/4.5-9. You can't scale up the focal length and not scale up the f-stop; the 'f/#' is literally a mathematical formula which includes the focal length. The t-stop doesn't change, but you can't alter the focal length in "focal length divided by" without also changing the result of that equation.
Same-old marketing intentional misleading.