Google paid for 3.5 Pro training. They just didn't release it.

They never gave an official answer as to why, so I'll let you draw your own conclusions.

They did not decide it wasn't worth spending the money to train.

They absolutely spent the money.

I work there. I have zero internal knowledge about the model. Opinion my own, etc. I don't think it is worth fighting to win on a month to month time horizon. When you step back and look an inch above this market, Gemini Pro 3.1 as a product was released in February. 6 months. It feels like forever and that Google is behind, but on a 2-3 year horizon? The models are going to stay similar.

Also, look at Flash 3.5 to 3.7. Flash 3.7 is a genuinely decent Sonnet 5 class model. Flash 3.7 is quite efficient too. Also, whatever was spent training 3.5 pro is probably not wasted. However, as a strategy, when I see models like Kimi K3, Fable, Sol. If you discard "because the model sucked" what other alternatives or potential options might exist?

I thought of a quite a few and they are far more compelling and interesting to me.

(Also Gemini models tend to be pretty decent at more than just programming. Enterprise AI use is more than just software eng / programming)

3.5 was almost certainly a 3.1 post-train, so likely a small investment on Google's part.

They mentioned that they have already started pretraining Gemini 4, which will be the full ground up rip-your-face-off-expensive training that is often discussed.