The default when running static languages like C++ or Rust or Go via Sulong is to stick to the memory layout chosen by the programmer. There is no conversion to typical JVM memory layouts. Nor does running on the JVM has major restrictions for the framework (we are working on a version that does not run on the JVM in the SubstrateVM project). What Graal+Truffle allows is for library writers and language designers to invent new representations without any restrictions on the layout and have them interact with the rest of the system. We want programmers to use the best language for the task. And even combine multiple languages within one program. Foreign objects can be passed around freely as parameters and local variables, but there are restrictions when building combined data structures - e.g., if you have a highly optimized native data structure, it is not possible to install a pointer to a JavaScript object in it without performance loss.