I think it's valve's tf2 developer having a great time trolling everyone.
I bet this is during their break, and everyone is watching him on the big screen they got at the office.
I call shenanigans.
Valve wouldn't cheat their own game for kicks and giggles. Nor would they nullify the pyro class by making all of their weapons fire retardant.
Well, I know I was the original one to call shenanigans, but turns out they are real. The moderators on the Steam forums confirmed that the Valve employees do have these, as shown in a few different videos of them playing.
Valve won't release these to the general public -.- Some servers may find a way to mod it to use these weapons, but unless you work for TF2 Dev team... you aren't getting these. Valve doesn't want to ruin TF2 yet, they are waiting for the demonman update.
no, they are real, its been confirmed on steam forums and you can got to Finol's community page, he is part of the 'Valve' group which is Valve's official group that only employees are in.