I've spent much more time on PerC than here, and that seems to be the case there at least?
Male 2s mistype at 8 because of the knight in shining armor complex and that male 2s tend to be very masculine, heroic and "I have no needs" and they feel like 8s because they're tough and strong and vengeful, but realistically heart-driven hot-blooded 2 vengeance is different than cold-blooded 8 vengeance. If a 2 male feels like he has a soft spot for women but he's a tough warrior, he might type at 8 because of his 'feeling like a warrior.' He mght mistype at 8 because he doesn't relate to the lovey dovey softie bullshit that is often in bad 2 descriptions. No real 2 would.
2s might mistype at 9 thinking they give in to the needs of others. Realistically they are power types giving the other person what they want so that the 2 will have power over them.

But they might not see that in themselves, and just look at the behavior of 'giving in.' 9w8s can do this for power to a degree, but it's less power-driven and goal-oriented and more "loss of sense of self" oriented. Less pride, more sloth, to put it simply.
But both mistypes are possible because of the commonality of 'giving in to the needs of the other' of 2 and 9, and the common prideful heroic badassery of 2 and 8. I've seen female 2s (in my humble opinion) mistype at 8 as well, because they think 2 is weak when realistically it is anything but.