Who told you that? You can write entire C libraries and call them from Electron just fine. Browser is a native application after all. All this "native applications" debate boils down to the UI implementation strategy. Maintaining three separate UI stacks (WinUI, SwiftUI, GTK/Qt) is dramatically more expensive and slower to iterate on than a single web-based UI with shared logic
We already have three major OSes, all doing things differently. The browsers, on the other hand, use the same language, same rendering model, same layout system, and same accessibility layer everywhere, which is a massive abstraction win.
You don't casually give up massive abstraction wins just to say "it's native". If "just build it natively" were actually easier, faster, or cheaper at scale, everyone would do just that.
Value prop of product quality aside, isn't the AI claim that it helps you be more productive? I would expect that OpenAI would run multiple frontends and that they'd use Codex to do it.
Ie are they using their own AI (I would assume it's semi-vibe-coded) to just get out a new product or using AI to create a new product using the productivity gains to let them produce higher quality?
It comes back to fundamental programming guidelines like DRY (Don't Repeat Yourself) - if you have three separate implementations in different languages for everything, changes will be come harder and you will move slower. These golden guidelines still stand in a vibe-code world.