Regardless of the actual merits of the dispute, if they overrule the ban, they'll be accused of penalizing an aggrieved underdog. The White House of course would really prefer not to get involved. Maybe they're bluffing, maybe they think they have the right cards. Their announcement that they're preparing to pull the devices from shelves is an 'all in' poker bet. Apple may feel they're in the right and flat out don't want to settle, or at least don't want to settle if the White House could overturn the import ban, knocking out Masimo's leverage. They figure the closer we get to the import ban going into effect, the higher the price they can demand from Apple, if Apple blinks. Masimo just wants Apple to give them money, to settle. The situation as described is a big game of high-stakes poker. 'No comment' doesn't really speak to the White House's intent.
