See: https://docs.google.com/document/d/1ifqtL09BTZOjBeiP_6h7ZBvRysmlqsxbmW9vYohkw-E/edit#heading=h.rxdo286pukcc

Payload definition

The first area is the payload of the micro releases. There needs to be a strict payload definition to assure predictability of the micro release delivery. To us this is a hard requirement when it comes to the maintenance phase, we should apply the same approach even when we are close to the end of the full support cycle. The payload definition of the micro releases in the maintenance should be controlled by GSS and PST.