Earlier quoted context omitted.
That's not what they said. A significant fraction (probably the majority) of Slack's functionality is server-side, not client-side. Even if the client were to be rewritten from scratch, you would not need to replicate 100% of Slack. But you also don't need to re-implement the entire client. You need to do a significant architectural change for performance improvements, not a complete overhaul. Reasonable people can d…
No, it's pretty warranted. The 100% I was referring to _was_ just for the clientside. To rewrite that natively (since today it's in js on Electron) is not going to take a couple of months with five engineers.
Hell, throw a few million at it and I can't see why Slack can't be implemented natively on at least iOS, MacOS and Android (especially if parts can still fallback on webviews).