Since you say that JAL is letting you switch, I'll presume that you are currently ticketed with JL flight numbers. My understanding is that if you change to longer routings (HND-DOH-ICN is certainly interesting!), the flight numbers of the bookings will determine the accrual. So if it is booked as QR flight NNN, the QR earnings rules would apply for that segment. One thing to keep in mind, though - JL has some very generous earning multipliers for Aadvantage, so depending on the class in which you are booked, some of the earning multipliers on QR-coded flights may not be as attractive.