Good point about code compiled to C++ not being the same as idiomatic C++ code.

However, unlike PHP which is dynamic, C# is statically typed. It is a much more direct match for C++, and performance should be pretty good.

But with that said, I think your point still stands, as there are still things like bounds checks in C# which would need to remain when compiled to C++, while idiomatic C# might not have those checks.

I wonder though if those bounds checks couldn't be disabled in some cases. Sandboxing isn't a concern on the Unity WebGL port, for example, since the browser provides that, so il2cpp code doesn't need to be safe in that sense.