Just a data point. I recently booked a 3 leg pass, that came to GBP 205 after taxes etc. Paying revenue per sector would have been over £300. I used ExpertFlyer to find the G fare availability with a Japan Point of Sale, then used the online website without issue to get the ticket. I allocated the ticket against my British Airways Executive Club frequent flyer programme. I got the Confirmation Email and e-ticket email within an hour of purchase. I wasn't bothered about seat selection, since all the flights were under 90 minutes long. I am a UK passport holder in this context, and I flew into and out of Japan on a revenue British Airways return pair of flights from London.

My first flight was ITM (Osaka) to Nagasaki, and I arrived extra early for the flight. At check-in the agent was super polite and helpful, and did scan my passport's photo page several times. As far as I could tell he didn't check my entry stamp and sticker (though I am very obviously a gaijin) and he didn't appear to check the BA flight, though the BA 125 ticket number on the PNR could have been electronically checked. He also processed my JPY 1000 confirmed upgrade to J class at the desk fairly swiftly. Fairly similar but faster processes on my other legs, however for the final leg the 767 was completely full so no upgrade was possible even after going through the standby process. I ended up in window seats in the 2 J class sectors, which is my preference, and on the economy sector on the last leg I ended up in 48G, which is the penultimate row on a 767-300 domestic, aisle seat off the central block, but I had the only empty seat on the aircraft next to me.

The BAEC credits came within a week. I got the expected 40 TPs for the two J class legs, and 10 TPs for the final economy sector, as per BA's own table for JAL.