Maybe so, but there's this benefit-of-the-doubt thing. If you were ripped off by some mom and pop dealer or pawn shop that sold you this bass as an Alembic for $1000, how would you feel getting accused of the crime that victimized you? Unless it's obvious that the person knows what they have and are trying to slide one by, I believe it's best to start with a friendly query to assess the situation.
Of course, when some ass responds to such a friendly informational query with a load of attitude, I sometimes regret the decision. I'll still play it that way, though.