I am a trial of the Freak Fortress 2 TX server, and as your friend said at around 4:36: this is a bad showcase of the glitch. I do not see anything wrong with the Gray Mann round. When you summon once, there is not a cooldown for every single other summon. You can change what kind of bots your want to summon. Normal, Sentry Buster, Soldier, Heavy, Medic, Pyro, and "MEGA" I believe. MEGA does not work. Normal works just like the administrator summon, Sentry Buster summons 3-5 smol sentry busters that cannot jump, and the other ones work by summoning one robot at a time.
If anyone else finds the Gray Mann round odd, please comment and shed some light because I don't really know myself. Even if this is a glitch, Gray Mann is really easy to counter with Medics and Spies.
EDIT: I just noticed this, where is the Panda-Community.com tag that should be at the bottom of the screen? I'm not trying to say that you're faking it, but it's something odd I noticed.