different text but same conditions...
"refundable in case of cancellation before flight departure" means the same thing (they are talking about the 1st flight). Note that this means you can't cancel the ticket once you've started travel (this is normal, though); so once you got to Europe, you can't cancel the CDG-LAX flight for full refund (but why would you want to do that?). In that scenario, they would *probably* re-price the journey the corresponding one-way LAX-AMS fare applicable on the date of purchase and refund whatever was left over from the amount you paid for the open jaw but don't hold me to that without seeing the full Fare Conditions.
Compare with the conditions if you don't tick the "Flex only" box:
