Or they know tooo much. I suppose a bright line at the edge of an element group looked at from the very very side might be construed as such, depends if you are selling it as mint or used. Almost every Duesenburg is technically a "salvage" or "rebuild".
Separation can look like a "soap bubble" at the edge or even center where there is a very slight void in the balsam or cement. Lenses older than 30 years sometimes had a little of this somewhere, or got some after a decade.
Look for "soap bubbles" sometimes people think, and it appears to be a coating blemish. A true coating blem would have less effect on the image formation than separation.
I agree with mr Finley too.