They're saying that the differences are secret, and they're not gonna release the specific structure of the LNPs and why the differences are there. The equivalent of having two proprietary binaries that both accomplish the same task, but have different code, and the reasons why are secret as well.
And we're accepting this on the first mRNA vaccine ever to be used on a massive scale, all to protect their profits before the rest of the world can start producing vaccines. Yes they spent a lot of money and time creating the vaccine. Now open source it and let the rest of the world save their citizens.