All 738s are now supposed to be showing the Kodiak configuration as of a certain date so it’s possible that even if the seat map didn’t actually change after your booking, some internal glitch associated with the change to all Kodiak impacted the seat assignments on your flight and while the system preserved MCE seats for your group, it didn’t automatically put you together even though there were open MCE seats. (Just like how when upgrades are processed, I’m never automatically seated next to my spouse, even when F is wide open?)