Apple had an update ready months ago to switch off the Apple Watch pulse oximeter
After having sales of the Apple Watch Series 9 and Ultra 2 banned in the US due to a patent dispute, Apple was able to put these models back in stores by switching off the blood oxygen feature. It was still somewhat unclear how exactly Apple was doing this, but 9to5Mac learned not only the method Apple has been using to limit the feature in the US, but also that this update was ready months ago.