Most Android manufacturers are using minimal development teams to get closed source blobs from the CPU+radios OEMs to talk to the OS. Like the article says, Qualcomm stop supporting older generations of their SoCs pretty quickly, and those manufacturers don't invest the resources in custom development, which is the LineageOS approach that Fairphone are taking. There's nothing to promise these updates will be stable and secure though.
Apple has a huge advantage in developing their own processors from start to finish. They're not reliant on anyone else's code, and if they do need to buy in certain components (like Intel modems that they've used before), they've got the size and budget to get pretty much anyone to agree to their terms. It's why Google started the Tensor project, which is rumored to be finally going full Google (ending reliance on Samsung) from 2025/Pixel 9.