I guess it really doesn't, just think it is a more likely scenario to deliberately assume a switch with someone to sit next to a travel partner. Not really important for what my question here is: How would you handle the situation if they didn't move so easily, given this is mid-plane during boarding and a FA is not near by.
I have definately used the flight attendant call button for this in the past, and they will be proactive in getting everyone to their actual assigned seat.
I had a flight where the flight attendant had to move my party out of bulkhead seats due to the FA placing some pre-board wheelchair users there, and that shuffle caused enough confusion to call her back to settle everyone out. Admittedly she said to use the call button so was aware of it from the beginning.