Thanks to everyone for the responses. I was able to compare my
Y-DNA DYS markers to that of the "genetic distance 3" person. Sure
enough, there was a difference (mutation) within the first 12
markers, so I now understand that disqualified him >from showing up
in my list of people with the 12-marker match. Beyond the 12
markers we were extremely similar.
This stuff is fascinating. Maybe years >from now much more of the
population will have had DNA testing and we can get a really good
sense of span of time between mutations. and other stuff.
With thanks to all,