Yes it does. The Department of Homeland Security answers this exact question:
TSA recommends passengers transferring at one of the 10 affected airports place any large personal electronic devices in their checked bags upon check-in at their originating airport.
Do note what the Washington Post says, quoting an anonymous source:
the logistics of enforcing the ban will be daunting, particularly in instances where passengers take connecting flights elsewhere in the world before boarding a plane bound for the United States.
“You’ve got to wonder, if somebody’s connecting and doesn’t have access to his checked bag to put his laptop in, what does he do?” the official asked. “I guess people will figure out that if you’re connecting in Casablanca, you’d better have your laptop in your checked bag.”
What if you are at the connection with an extremely threatening ebook reader you forgot to check in? I imagine the possibilities will include:
- Gate checking a bag. If they have the facilities to do so, if you have a bag and so forth. In the best case, the affected airports will make thick cardboard boxes available for gate check purposes perhaps for a fee. If they really want to serve you well, they might even add an air cushion machine. Packaging fragile items is a problem with known solutions. Gate checks involve less baggage handling so the chances theft are somewhat lower but still, those boxes might as well have a meter high sign on them with thick letters screaming "valuable items!". Edit: On March 23, 2017 Emirates indeed announced this option.
- Mailing it. (Although AFAIK these facilities are typically landside which makes it problematic and time consuming to get there unless you are escorted there and back by security to bypass immigration going out and normal security coming in...)
- If you have a lot of time perhaps they will be lenient enough to reunite you with your checked luggage briefly which, again, quite probably will require security presence.
- Rerouting through the EU or Canada. I would find this extremely unlikely for cheap economy tickets but who knows.
- Finally: not boarding the aircraft to the USA. I suspect in this case they will make you buy a ticket back to your starting point or wherever else you want to go. Again who knows what happens to business (or first) passengers.
Actually, the airlines went beyond my imagination: Qatar Airways and Etihad Airways offer loaner devices for business travelers and I bet Emirates won't be far behind.