If what your saying is that every pin x pin crossing will always 100% give pins, then I have no way to explain it, and there is something much bigger going on with the pinstripes, perhaps some other trait is closely linked to pins, with a probability of 99.999~%.

Are there people with proof that ANY pin crossed with a pin produces 100% pins? I would really like to know. That would decide that there is something definitely going on with those pins and spiders. And apparently, they inherit traits differently than everything else.

But if it helps to understand, call the pinstripes from a Pin x normal cross, het for normal.
If those het for normal pins are crossed with each other, the same punnet's above still apply, and you should theoretically get 25% chance of normals.

I still theorize that the homozygous form of pins are probably lethal. I have no proof, and people will call me crazy, but I can see no other way around this.

But if there are people with the proof of any pin x pin crossing produces 100% pins in a litter, then my whole theory is shot.

There's another project to add to the list, homozygous lethal pins.