Yes, I think we should understand that this is what Andrew says, so e.g. "This type of optimization, Andrew explains, would not be possible in languages like Rust" is akin to when football players tell you they're confident they can win. Of course they're confident they can win, but at least half of them are going to be disappointed.

I actually don't know what Andrew is getting at with that particular case though. If the situation is that the types are obvious, so the Zig isn't ever looking at the tags, the Rust won't look at the tags either. Worse, I don't think Zig has niche optimisation, so there are a bunch of cases where Zig has to choose, have tags (more space, slower, but same safety as Rust) or go without (same size as Rust, but less safety). Rust only guarantees the niche in certain narrow cases like Option<&T> (is the same size as &T) but it actually delivers a lot more than that, and this continues to improve.