Why does this only affect the newest model?
This is apologist. Masimo claims, and multiple court cases have agreed that Apple did, in fact, use patented technology without payment (and frankly, even as an all Apple person, their behavior in this whole situation was entirely shitty).
Couching this all as “claims” gives Apple a benefit of the doubt, similar to the people who refer to Masimo as “nothing but patent trolls”. Previous discussions here had multiple people referring to them being “butthurt that Apple hadn’t offered to acquire them”, or that they “lacked the product chops to bring their own solution to market”.
Also AFAIK Masimo didn’t just want to be paid they wanted to have some direct on the development of Apple Watch.
Also… the patents themselves seem like a joke and shouldn’t be valid.
They had concerns about some of Apple's design and functionality decisions around the sensor on the watch. They didn't want their technology to be associated with a poorer user experience...
... you know, kinda like how Apple has a whole review process and has input on the development of your apps for their platform?
Conflating that as "they wanted to be have some direction on the development of the Watch" is a notable exaggeration.
[1] https://ipfray.com/u-s-trade-agency-itc-incredibly-portrays-...