I'm pretty sure it is widely known that the early 5.x series were built from 4.5 (unreleased). It seems more plausible the 5.x series is still in that continuation.

For some extra context, pre-training is ~1/3 of the training, where it gains the basic concepts of how tokens go together. Mid & late training are where you instill the kinds of anthropic behaviors we see today. I expect pre-training to increasingly become a lower percentage of overall training, putting aside any shifts of what happens in each phase.

So to me, it is plausible they can take the 4.x pre-training and keep pushing in the later phases. There is a lot of results out there to show scaling laws (limits) have not peaked yet. I would not be surprised to learn that Gemini 3 Deep Research had 50% late-training / RL