I also have a few that I carved and left unfinished nor sanded, but they haven't been smoked nearly as much as my Nording. This is interesting though. This is the first time someone has said that the stains come through in such a way. Fascinating. I am just curious if anyone else has experienced this with their own unfinished pipes.
Even when I see other people's unfinished, they aren't spotted or speckled with tar, just slightly different, which could be from oils on the skin also.
All of the evidence says that the briar doesn't breath or... the cake doesn't even go beyond the surface also. Just amazing if this throws all of that out the window, and we're left with speculation again.