When I opened a Rust project I think the status bar said it was downloading Rust support, which supports your hypothesis. (Also it doesn't make much sense to bundle these things when they are all making new releases at different schedules.)
size /Applications/Zed.app/Contents/MacOS/zed
__TEXT __DATA __OBJC others dec hex
120979456 475136 0 4336828416 4458283008 109bc0000 zed (for
architecture x86_64)
117587968 458752 0 4336680960 4454727680 10985c000 zed (for
architecture arm64)
Then, each of these binaries includes about 40MB of assets. I've actually had a PR up (https://github.com/zed-industries/zed/pull/3997) that reduced their size quite significantly, though that did not end up reducing the size of a .dmg itself, so I've scraped that.
On top of that, we ship with debug symbols for symbolication of crashes (https://github.com/zed-industries/zed/blob/main/Cargo.toml#L...).