Now, having looked into both sides of this.
At no point was the stock ever presented as a genuine Magpul stock: I re-checked the sales thread and it was labelled as a clone from day 1;
Reviewing the video (Infernau's) there is indeed signs of normal wear from mounting, but I saw nothing (nor did you point out anything) to support the claim of "damage";
Relating to the above, Alex Umil's claim it was "new" (even if it was in good condition) was misleading;
An attempt to mediate the situation was attempted, to which Infernau replied something along the lines of "forget it the guy's a douche" (as I was simultaneously in contact with Alex, I know there was a possibility of compensation);
How this is now being presented as being genuine Magpul vs Element repro strikes me as a complete scam: Infernau, whatever your next post is, I would seriously think twice about what it's content will be.
Either way, Alex Umil had been previously warned and has had his AV status revoked due to an unrelated dispute.