Kind poster, I understood about 4% of what you wrote and absorbed 2% (entirely not your fault). Would you say that this explains why Google only supports their Chromebooks for 5 years?
ETA: My question is based on what you wrote here:
Linux has LTS releases that are supported for 6 years. They release a new LTS every year. Each year, Google selects the latest LTS and builds the latest Android version against that release. They can add to the KMI when this happens, but it is frozen for that kernel version from then on. From there, they keep building Android against that kernel version until it is no longer supported.