A GA saw three together and a pair of unconnected so they moved you aisle for aisle and window for window (and probably middle for middle for 3E) and then put the three together. If you weren't actually travelling together - which is the case for most people on different PNRs - then you probably wouldn't have cared at all, except for the EML seats that include row 3 now.
Or they bought 3 EML seats and you got moved to accomodate since you didn't.
That's my guess.