I'm flying on the Heathrow route in December, and noticed JAL automatically changed my economy extra legroom seat (row 23) on the 777 to a non-extra legroom seat (row 46) on the A350.

I managed to change it to extra legroom exit row 45 manually, but it made me realise that there's only one extra-legroom row on the A350 versus two on the 777, which is a bit of a step down for economy passengers.

Those who aren't quick to manually change their seats due to the change in aircraft will miss out.