It's not a theatre dominator by any means. But it will throw a glut of premium (and coach) seats all over whatever routes it can do. Add up the number of FC and coach seats per year from JB and you can't deny the significant impact that will have on yields. That's the point.

Competing with like metal or not also isn't the point. Sometimes loss leaders have to be fought with more severe loss leaders because sometimes you have to spend money to make money. Allowing a competitor to poach anything off your menu they want on their terms whenever they want to "preserve yields" is guaranteed to be a losing stratedgy.