Comment by Rohansi

That's true but I haven't seen word from them on what is changing with IL2CPP. They've already confirmed that there are no plans to use CoreCLR's superior GC in IL2CPP so they could also just not support the intrinsics so it falls back to scalar operation. IL2CPP support is an important detail because many of the platforms Unity targets only work with IL2CPP and Unity recommends IL2CPP for release builds on the rest.