It's certainly all right for the player to say that he thought that the ball crossed between pine tree A and oak tree B. We then can, in good faith, "estimate" a crossing point. I can say that in my years as a Rules Official I have never had a player say that the ball might have gone in over here near pine tree A or maybe it went in over there near oak tree B so how about we split the difference? No one is that clueless.
So I guess you have never encountered an irregularly shaped hazard like the one Fourputt described, or in my case, lost sight of a ball while it was travelling PARALLEL to the hazard. The reason I said it could be point A or point B (or in between) was that points A and B stuck out a bit so if my ball that was travelling parallel to the hazard when we lost sight of it and took a slight kick to the left, then it would have entered either at A or B with a harder (unseen) kick to the left needed for it to enter in between the points.
I have less than 20/20 vision (even with contacts), but I am not stupid. Sure, I could say that it went in at point B and call it a day, but that wouldn't be honest. Prior to searching, I was very hopeful that the ball was NOT in the hazard, so how can I then turn around and say it MUST have gone in at point B? Uncertainty of the entry point seems pretty natural to me given that the ball was travelling PARALLEL to the hazard when we lost sight of it- being that the ground is pretty flat, how would you deduce the entry point?