Throughout his entire career, almost all of Edmund McMillen's games have been brutally difficult. I wouldn't even argue that Super Meat Boy was the most difficult game he's made.
Not to mention that, for as difficult as it was, it was completely fair and was excellent at teaching you the game's mechanics. It never threw a challenge that can't be overcome and you haven't been taught to overcome. And, at worst, death was a minor inconvenience. The End is Neigh- Edmund's newest game -is just as challenging as Super Meat Boy.
So I'll have to say that it definitely isn't why.