In almost all cases knowledge of copy-on-write doesn't have to be widespread because it is equivalent to value semantics. It is only because they were using a

In almost all cases knowledge of copy-on-write doesn't have to be widespread because it is equivalent to value semantics. It is only because they were using a buggy dll (which for non-matlab users, is custom native code that matlab calls against using a FFI), that the expected semantics of matlab were violated.