> ...all that dictates the release schedule.

AI companies release models when they are ready - not on a set schedule. The steps are required to produce a release candidate, so a company can choose to bless the RC with the best metrics at any time - or alternatively continue (post/)training newer RCs if they feel they can do better, and they have time. When a model is ready for release is subjective, and can take into consideration what the competition is doing.

An obvious counter-example to schedules driving releases is the still unreleased Gemini 3.6 Pro.