Back when my little linnie was still alive (gods rest his soul---I was away and my dad called to say he found him feet up in the air on his back

) he probably was the only one out of the three birds I've owned as a young adult/teen who drew blood when he bit down. He was also the only food aggressive bird I had too.
I'd wager the new world birds are feistier than the old world birds like what I was used to with Jacko and with the cockatiel. The hardest bites I've ever gotten from Jacko only slightly broke the skin but in that weird not deep enough to bleed sort of way---and believe it or not those bites were NOT directed at me---she was in overload from trying to attack something (like a broom or the cockatiel) and I happened to interrupt her attack and get in the way. Even then she clamps down and chews (makes the exact same sound as her gnawing on a rope toy---freaks me out!) but never makes me bleed.
I might either just a) have a particularly sweet natured grey or b) stone skin and dumb luck of course but Jacko never really full out bites, she'll give me a pinch or a quick jab like a snake would but she prefers to fly away or posture (lots of fluffing and beak banging and antics).
This has been a constant in our relationship and to this day she only rarely bites (ie I might get a little pinch once a month at worst and usually its because I was stupid and did something I *know* she wouldn't let me get away with).