Tawshīʿ begins by announcing two unnamed matters and subsequently names them. In specific-after-general, the specific member is already included in the preceding general expression; the second mention highlights its importance.
FormInitial expressionBenefit
TawshīʿAn unspecified dualTwo names resolve the ambiguity
Specific after generalAn inclusive general termSpecial attention to one member
The fact that an expression is mentioned twice does not collapse the distinction between the two devices.