I am not 100% sure this is the right thing to do. We need to investigate further whether SAC_MT_SYNC_FOLD really is no longer needed (which I believe). If that truely is the case, we can get rid of that ICM and its generation in compile.c completely!
I am pretty sure that none of the three main WL operators (genarray, modarray, and fold) need this. fold-WLs seem to end up with inout parameters (in for neutral and out for the result) and genarray and modarray typically have non-scalar returns enforcing them to be inout as well.
Further investigation is being asked for!