I think 'scope ref' should always pass the address of given argument to the function body. Because 'ref' always means "pass the address of given argument". So, if given argument is an rvalue, compiler will allocate a temporary on stack, save the rvalue in it, and take its address. If argument is an lvalue, take its address directly. It should be always true, eve if the parameter type is small int.
Essentially language semantics should not reflect low level implementation detail. After DIP36 is accepted, we will get a full set of tools for efficiency - T, ref T, and scope ref T. From the toolbox, you can choose the most efficient storage class based on the T.
void foo(MostEfficientParameters!(int, string, S, int[1024]) params) { ... }