That is situational. Preferably people don't lie. However, nuance can make it inevitable.
I once watched an anime called Usagi Drop. In it, the oldest member in an enormous family, who was in his eighties, ends up, ahem, "going around", and he dies having fathered a girl, who, in the big picture of the family's family tree, is the great aunt of several of the characters who are well into adulthood. Japan is a nation that considers such matters highly controversial and stigmatized, and this was a major plot point in the show. The young adult characters decide it's best to "adopt" her and not reveal her origins as a form of protection. Would totally recommend the anime nevertheless.
Can you imagine if the Allies were fighting the Axis powers, and while making the ghost army, the Allies were like "yeah, those tanks are inflatables, it's Normandy we'll be going after"?