CPP13 — _var's and valuetypes

1.9.1 says:

"The copy constructor deep-copies any data pointed to by the T_var constructor
parameter. This copy will be destroyed when the T_var is destroyed or when a new
value is assigned to it. Compliant implementations may, but are not required to, utilize
some form of reference counting to avoid such copies."

and

"The normal assignment operator deep-copies any data pointed to by the T_var
assignment parameter. This copy will be destroyed when the T_var is destroyed or
when a new value is assigned to it. Assigning a null pointer to a T_var is legal and
results in deallocation of the data pointed to by the T_var."

So my question is, is it legal to use ValueBase::_add_ref() and _remove_ref() instead of _copy_value() in this instance when T_var is representing a valuetype?