I know some of you will be shocked to find me arguing on what could be seen as the Tesla side of this, but I think it is entirely possible Tesla just hasn't released the full capabilities of Ludicrous Mode on the P90D's with Ludicrous yet. (I'm not defending that action--just suggesting it as a possibility.)
Tesla kind of has a history of doing stuff like this.
All the P85Ds were released with torque sleep completely not yet enabled. Everyone was wondering what the heck was wrong with the cars' efficiency, because it wasn't close to what was promised. There was a lot of discussion, and wk057 was out doing a side by side video comparison with a P85 when the blog post explaining that torque sleep wasn't enabled yet was published. That was roughly three weeks after deliveries started. It was terrible communication and terrible customer service, for no good reason. A simple explanation at delivery time like, "Oh, just so you know, torque sleep isn't enabled yet, so you won't get the efficiency that you may be expecting, but it's coming soon.", would have completely eliminated the issue. Tesla had to know people would notice. It was just a bad, bad decision on how to handle the engineering delay on Tesla's part.
We know Tesla is lousy at this kind of communication. Lousy is an understatement. They're terrible at it!
I believe many people think Tesla also likes to test things in small batches, and in small increments when pushing the limits. It would be reasonable, then, to think that perhaps a few cars are fully enabled with Ludicrous capabilities, while most are not. Or maybe none are yet. But it would be completely consistent with how Tesla operates to deliver Ludicrous cars that aren't really fully Ludicrous yet, and not say a word about it.
I am optimistic that P90Ds with Ludicrous will get into the 10s in the quarter mile eventually, as a result of software updates.