You are confused. No point in pushing this in any further. The M400 more than delivers its rated specs. It's not a debatable point; it's a fact.
They don't double down to 2ohms as you first wanted readers to believe, with these figures you posted
D'Ag does exactly the same thing. My M400s:
400 watts @ 8Ω
800 watts @ 4Ω
1,600 watts @ 2Ω
As I said they come close with these being the tested figures
405W into 8 ohms
640W into 4 ohms
1115w into 2 ohms
And are still a good indication they can deliver good current, it not a debatable point it's fact as independent measurements confirm.
Cheers George