Bias circuit impedance rule of thumb: 10x the Impedance of Drain/Output Matching?

To avoid loading the output matching network, there is a normally rule of thumb by which the bias circuit impedance should be in relation to impedance at the drain and matching network.

Is this 10X refer to the magnitude of Impedance

or

10X the real part of the drain/matching network impedance?

Normally for PA, the optimum real load resistance is around 1-2 ohms. The reactive part is cancelled in the matching network...