Agreed. I would even call such initiative premature optimization, with unknown gain compared to just optimize the WebView component in the native shell if that's ever needed. More so for any new startup trying to enter the KMS space in general.

I don't think Notion need to worry about FB. I think Notion might need to be worried about the potential market saturation caused by how easy it will be for a small team of 3 to clone Notion (and all of its integration, API, and so on) on all platform perfectly in a weekends. At that point, it's not the technology bottleneck anymore but more so a battle over branding and minor UX improvement.