Exactly.
When they made the changes to the s boxes for differential cryptanalysis resistance the entire concept of that was essentially secret, so who knows what they know about elliptic curves.
Again, Koblitz and Menezes take this idea on directly in their paper. But I mean, at this point, nobody serious is going to take the P-curve seed conspiracy theory seriously ever again.
The number of weak classes of elliptic curve would have to be gargantuan for this specific search to produce some. If that many curves are bad, then ECC was a mistake.