Hello,
The impedance of 73 + j42.2 Ohm is for an infinitesimally thin half-wave dipole, that is, a dipole with zero thickness (zero radius for a cylindrical antenna). Then, this value is obtained theoretically by a limit process in which the dipole cross-section tends to zero. The values around 90-95 Ohm in the input resistance is then due to the finite thickness of the dipole. It can be demonstrated that the input resistance is more affected by the "finite thickness effect" than the input reactance.