Crazy wild rumor about a new 400-800mm f/8.0 GM lens

Guys, it’s vacation time and I need a break. So I figured I’d take the chance to post this crazy rumor I received from an anonymous source. I give it 0.000001% that it’s true. And I wonder why such a lens makes any sense at all! The “source” wrote:

The zoom lens is a FE 400-800 with large aperture values such as F8, I have seen it being used in the wild. Best Wishes.

For sure this would be a novice as nobody ever did something like this. But f/8.0 constant aperture? Would that be even interesting for someone?