IDynamicMetaObjectProvider mostly just caches and returns System.Linq.Expressions for various asks, so again most of the JIT awareness is still just System.Linq.Expressions awareness.

The COM support is by implementing IDynamicMetaObjectProvider in a cross-language reusable base class.

The C# `dynamic` keyword adds some smarts about IDynamicMetaObjectProvider to the C# compiler, but those smarts were never seen to be needed as a low level tool in the CLR itself. And again, once the C# compiles the IDynamicMetaObjectProvider calls, those mostly just result in System.Linq.Expressions for the JIT compiler to optimize in the same way it optimizes other usages of Linq.