The 22-250 neck shoulder junction is about .110" (deeper) longer than the 223. So the larger 22-250 die could allow the case to be off center as the bullet started into the neck as it would be unsupported at the start. You could get some major runout, which hampers accuracy. Do you have a runout gauge so you could load a few with each die and see if there is a differance?
I can also see the bullet tiping sidways a little too much and hit the shoulder area of the die and kink the neck. The 22-250 body area is a bit bigger than the 223 and it would happen quicker than in a 223 seating die.