At the 18:30 mark, a different necron player is able to spawn a real monolith without losing his HQ, giving him a total of four HQs. After creating a real mono gltich, he tries to create fake monos but they die like they should. I'm guessing this player just learned about the gltich and was unaware you couldn't create fake monos that stick around.
Normally when one creates a mono from their HQ, just before it pops out it is accompanied with some graphic transformation animation and some sounds. None of that is present when this glitched real mono is created.