Very cool find. I think Sunday the 27 is the traditional start of winter season, right?

Quite a lot of repositioning happening on the 26th. From JFK that day, 4x widebody to MIA, 1x to CLT, 1x to DFW. I'm sure people can find others.

If the flight sticks, OP my best guess is that you eventually get moved to J. All these repositionings are loaded as 2 cabin Y & domestic first (J) and no one has realized yet that they do sell 3 cabin between LAX-JFK. But maybe that never happens, so might as well leave as-is and hope for the best!