Screening
Everybody here is IMHO wrongly focusing on the devices, but the fact that specific airports are targeted suggests to me that there are serious doubts about the integrity of the security screening personnel at these specific airports.
The fact that specific airports are mentioned versus a worldwide ban, means that the authorities believe that any potential terrorist with a weaponized laptop or tablet will be stopped when trying to board a flight from the EU to the US or vice versa from the US to the Middle East.