Sure it doesn't do placement new yet, but I think you're exaggerating the effect on lack of copy elision. Rust doesnt really need copy elision so heavily because it defaults to moving stuff, and move is just a very shallow copy taking typically one or two cycles. I've never seen it become visible in a profile.
In C++, copies are much more heavy, because they need to preserve the original, so copy elision matters a lot more. Also a developer is free to put arbitrarily complex stuff into a copy constructor. In Rust, those heavy copies are explicit so the developer can fully control when they happen.
Nevertheless - it could be all those reasons together. It's good someone is looking into it.
eh? Rust doesn't have placement-new or specify copy elision. nothing at all to do with backends or "code style".