Actually, we do not all know that. Properly done, there is no reason that pinning will not work just fine. The study from, I think Ford, indicated it to be a better long term solution, but the long term involved was so far past the lifetime of the car that there was no practical difference between a good weld job and a good pin job other than cost, which is why welding has been the more common solution.
The start post for this thread was posted twice, and since all the responces are in this one, I will delete the other.
pax, smn