For starters, logic doesn't work this way at all. Counterexample doesn't make a valid argument against non-absolute statement. And the claim is that in-browser code can be as performant as natively compiled (as you conveniently quoted). So apparently building the case on Discord misses the point twice.

Also for the sake of correctness: Discord CTO said the Rust-based app with 2 accounts uses around 290 MB which is significantly more than even the first empty tab uses (and each of the next will use smaller amount due to sharing).