I was convinced of this line of thinking for a while too but lately I'm not so sure. In software in particular, I think it's actually quite relevant what you can do in-house with a SOTA model (especially in the tool calling / fine tuning phase) that you just don't get with the same model via API. Think Cursor vs. Claude Code -- you can use the same model in Cursor, but the experience with CC is far and away better.

I think of it a bit like the Windows vs. macOS comparison. Obviously there will be many players that will build their own scaffolding around open or API-based models. But there is still a significant benefit to a single company being able to build both the model itself as well as the scaffolding and offering it as a unit.