Well look, Top Gear isn't exactly water-tight at secrets ... the Stig's identity did get out after a while, after all.
Also, with such exclusive vehicles, I'm pretty sure the manufacturers have very good ideas regarding where they are at any point.
Finally, it's just a question of risk: to these owners, even if there was only a 20% chance that the manufacturer could figure it out, WOULD they risk it? Bearing in mind, car owners in this league probably didn't get this rich by embracing risk, and also probably get tired of their cars when the ashtrays are full (so to speak) ... a ban on car purchases is a very serious threat.
Frankly, I couldn't give a damn. Give it a year, and we'll all be drooling over these cars' replacements, so it's all good. Like it's been pointed out here, Ferrari probably knows very well that they've got no hope, and they don't want to be dealt the marketing blow to their halo vehicle.
Soooooo ... let's just skip to the hypothetical end-game.
And now we can all sleep easily