And that's just on their models. They'd also get (at the very least) signals on their direct competition, if not straight up prompts+completions as well.
All they really see as a model provider is little fragments of the picture, like trying to reconstruct the Mona Lisa by knowing which paint swatches Leonardo used.
In other words, they only saw whatever Windsurf sent as context with a "fix the bugs" prompt stapled to it.
By owning Windsurf, they see the entire source code of what's being built, all the time, plus how the model is interacting with it.
There's a massive amount of value in what happens client-side, and behind the scenes. The "director's cut" of context.
Huge difference.