wannabe... I did notice the same diameters. After a few attempts to get through to AWC (American Wood Council), first through phone, then through the protocol email for inquiries, the final answer was thus:
The tables are based on an assumed penetration of 10 fastener diameters. A 12d common has the same diameter as a 10d common so their tabulated values would be the same.
Further, through the correspondence(s) they provided the following link to AWC's online connection calculator: (for what it's worth)
I was checking my own nail calculator spreadsheet against the AWC connection calculator and noticed a minor discrepancy. After double checking all my calcs I determined that the AWC calculator is not taking into account the tapered tip assumptions. I then emailed their technical support and the promptly responded that their calculator is based on the 2005 NDS and does not take the tapered tip assumption into account.
This only appears to affect two of the yield modes, but I thought I might point this out.
A confused student is a good student.
Nathaniel P. Wilkerson, PE