Not sure I'll get an answer quickly enough for it to matter, but on my flight ORD-LHR, 8A-H are shown as MCE, but 8J-L are shown as preferred (with standard legroom, favorable location). Is there a difference in those 3 seats vs the rest of the row?

I'm not sure if that's a change because up until a week or so ago, those 3 seats were not available to choose. Now that I'm checking in, they're all available and not MCE.