If Masimo hadn't finalized the patent, Apple would have filed it's own similar one and the reverse would have happened. It was literally their only option when confronted with a tech giant who is notoriously litigious. If that happened, Apple would have shut down an actual medical device company through constant legal battles Masimo couldn't afford to win.

This isn't trolling because Masimo is actually using the patent and the patent is specific. Patent trolling is filing a bunch of broad patents and hoarding them, often with no intent to develop a product, for the express purpose of either filing law suits or to stifle competition. Apple is often considered a troll for that latter reason.

Masimo would likely allow Apple to license the patent. But Apple tried to bypass paying licensing fees entirely and it's still doing so. Masimo was well within it's rights to protect itself from Apple, though. Unfortunately, this is what a smaller company protecting itself from a larger one looks like in the US.