Is it risky to use the system handles returned by load_system and open_system?

When using load_system or open_system to load a Simulink system from file, a handle is returned, and for all programmers that do not like hassling around with string identifiers and cell arrays for various reasons, this comes in very handy. Also it's the normal behaviour of functions loading or initialising access to a files content, like fopen, to return a handle. But unfortunately the returned handle is undocumented with load_system and open_system. Is this just a lapse in the documentation or does it mean that future versions of Simulink might have these functions return nothing or even something else (like a Simulink.BlockDiagram object)?