Doesn't this usually fail because of letting status pax board first? In theory boarding window-middle-aisle makes sense, but in practice if you let your elites board first and they are seated in random spots then you lose much of the efficiency gains. At least, that's been my experience on UA, but then again almost everyone gets to pre-board for one reason or another on UA these days (e.g., just signing up for their credit card puts you ahead of the regular boarding). Maybe LX can make this work if they restrict pre-boarding to a much smaller group of pax.