So, just today I was able to watch the video, so I may be late to the party but I wanted to had something, they keep asking what could get a primarch erased. Did they forget we actually have a decent idea? As in the emperor actually wanted to do the same with Lorgar but what stopped it was the other primarchs voting no, which lead to Monarchia burning, so at least we know that what Lorgar did gets you considered for that.