It might be my fault... The DLR interpreter got rolled into .NET native so that ETs could be interpreted (hence the weird EETypeRva:0x01588388 error). I actually did the initial set of work on that having had experience w/ the DLR interpreter and handed that off to the .NET team. I probably did the expression quoter but I don't quite remember :(

One thing I'll point out though, it's a Field on StrongBox<T> for correctness not performance - the field needs to be capable of being passed by reference to get consistently correct semantics. That's simply not possible on .NET native using the interpreter so it will end up with copy in / copy out semantics (which could break people but it's pretty unlikely). Also StrongBox<T> pre-existed the DLR expression compiler and was originally added w/ LINQ's ETs in 3.5 so we were also just re-using what they had already done. IronPython actually had Reference<T> early on which grew into the DLR's version and then finally converged back on StrongBox<T>.